diff --git a/source/blender/blenkernel/BKE_curves.hh b/source/blender/blenkernel/BKE_curves.hh
index 1f0d5c3b20f..b9a7da58a35 100644
--- a/source/blender/blenkernel/BKE_curves.hh
+++ b/source/blender/blenkernel/BKE_curves.hh
@@ -865,13 +865,16 @@ int calculate_evaluated_num(
 int knots_num(int points_num, int8_t order, bool cyclic);
 
 /**
- * Copies custom knots into given `MutableSpan`.
+ * Depending on KnotsMode calculates knots or copies custom knots into given `MutableSpan`.
  * Adds `order - 1` length tail for cyclic curves.
  */
-void copy_custom_knots(const int8_t order,
-                       const bool cyclic,
-                       Span<float> custom_knots,
-                       MutableSpan<float> knots);
+void load_curve_knots(KnotsMode mode,
+                      int points_num,
+                      int8_t order,
+                      bool cyclic,
+                      IndexRange curve_knots,
+                      Span<float> custom_knots,
+                      MutableSpan<float> knots);
 
 /**
  * Calculate the knots for a curve given its properties, based on built-in standards defined by
diff --git a/source/blender/blenkernel/BKE_curves_utils.hh b/source/blender/blenkernel/BKE_curves_utils.hh
index 47be4e2f656..f7f66702238 100644
--- a/source/blender/blenkernel/BKE_curves_utils.hh
+++ b/source/blender/blenkernel/BKE_curves_utils.hh
@@ -560,6 +560,43 @@ void write_all_positions(bke::CurvesGeometry &curves,
 
 }  // namespace bezier
 
+namespace nurbs {
+
+/**
+ * Gathers NURBS custom knots of selected curves from one `CurvesGeometry` instance to another.
+ * Should be used to implement operator's custom knot copying logic.
+ * `dst_curve_offset` can be used to append knots to already existing ones in the `CurvesGeometry`.
+ */
+void gather_custom_knots(const bke::CurvesGeometry &src,
+                         const IndexMask &src_curves,
+                         int dst_curve_offset,
+                         bke::CurvesGeometry &dst);
+
+/**
+ * Overwrites `NURBS_KNOT_MODE_CUSTOM` to given ones for regular and cyclic curves.
+ * The purpose is to to update knot modes for curves when knot copying or calculation is not
+ * possible or too complex. Curve operators not supporting NURBS custom knots should call this
+ * function with `IndexMask` `CurvesGeometry.curves_range()`, if resulting curves are created by
+ * copying all attributes. This way `NURBS_KNOT_MODE_CUSTOM` values might be copied though custom
+ * knots not.
+ */
+void update_custom_knot_modes(const IndexMask &mask,
+                              const KnotsMode mode_for_regular,
+                              const KnotsMode mode_for_cyclic,
+                              bke::CurvesGeometry &curves);
+
+/**
+ * Copies NURBS custom knots from one `CurvesGeometry` instance to another excluding
+ * `exclude_curves`.
+ * For excluded curves with `NURBS_KNOT_MODE_CUSTOM` knot mode is overwritten to
+ * `NURBS_KNOT_MODE_NORMAL`.
+ */
+void copy_custom_knots(const bke::CurvesGeometry &src_curves,
+                       const IndexMask &exclude_curves,
+                       bke::CurvesGeometry &dst_curves);
+
+}  // namespace nurbs
+
 /** \} */
 
 /* -------------------------------------------------------------------- */
diff --git a/source/blender/blenkernel/intern/curve_nurbs.cc b/source/blender/blenkernel/intern/curve_nurbs.cc
index 796f479793a..de6703e2929 100644
--- a/source/blender/blenkernel/intern/curve_nurbs.cc
+++ b/source/blender/blenkernel/intern/curve_nurbs.cc
@@ -52,10 +52,10 @@ int knots_num(const int points_num, const int8_t order, const bool cyclic)
   return points_num + order;
 }
 
-void copy_custom_knots(const int8_t order,
-                       const bool cyclic,
-                       const Span<float> custom_knots,
-                       MutableSpan<float> knots)
+static void copy_custom_knots(const int8_t order,
+                              const bool cyclic,
+                              const Span<float> custom_knots,
+                              MutableSpan<float> knots)
 {
   knots.slice(0, custom_knots.size()).copy_from(custom_knots);
   if (cyclic) {
@@ -112,6 +112,24 @@ void calculate_knots(const int points_num,
   }
 }
 
+void load_curve_knots(const KnotsMode mode,
+                      const int points_num,
+                      const int8_t order,
+                      const bool cyclic,
+                      const IndexRange curve_knots,
+                      const Span<float> custom_knots,
+                      MutableSpan<float> knots)
+{
+  if (mode == NURBS_KNOT_MODE_CUSTOM) {
+    BLI_assert(!custom_knots.is_empty());
+    BLI_assert(!curve_knots.is_empty());
+    copy_custom_knots(order, cyclic, custom_knots.slice(curve_knots), knots);
+  }
+  else {
+    calculate_knots(points_num, mode, order, cyclic, knots);
+  }
+}
+
 Vector<int> calculate_multiplicity_sequence(const Span<float> knots)
 {
   Vector<int> multiplicity;
diff --git a/source/blender/blenkernel/intern/curves_geometry.cc b/source/blender/blenkernel/intern/curves_geometry.cc
index ad8a6f36b5f..c0b2042c265 100644
--- a/source/blender/blenkernel/intern/curves_geometry.cc
+++ b/source/blender/blenkernel/intern/curves_geometry.cc
@@ -774,15 +774,14 @@ void CurvesGeometry::ensure_nurbs_basis_cache() const
         }
         const int knots_num = curves::nurbs::knots_num(points.size(), order, is_cyclic);
         knots.reinitialize(knots_num);
-        /* Some curves edit tools might not support custom knots, for example GP extrude.
-         * These tools create empty `custom_knots` with mode NURBS_KNOT_MODE_CUSTOM. */
-        if (mode == NURBS_KNOT_MODE_CUSTOM && !custom_knots.is_empty()) {
-          bke::curves::nurbs::copy_custom_knots(
-              order, is_cyclic, custom_knots.slice(custom_knots_by_curve[curve_index]), knots);
-        }
-        else {
-          curves::nurbs::calculate_knots(points.size(), mode, order, is_cyclic, knots);
-        }
+        curves::nurbs::load_curve_knots(mode,
+                                        points.size(),
+                                        order,
+                                        is_cyclic,
+                                        custom_knots_by_curve[curve_index],
+                                        custom_knots,
+                                        knots);
+
         curves::nurbs::calculate_basis_cache(
             points.size(), evaluated_points.size(), order, is_cyclic, knots, r_data[curve_index]);
       }
@@ -1589,6 +1588,15 @@ void CurvesGeometry::remove_curves(const IndexMask &curves_to_delete,
   *this = curves_copy_curve_selection(*this, curves_to_copy, attribute_filter);
 }
 
+static void reverse_custom_knots(MutableSpan<float> custom_knots)
+{
+  const float last = custom_knots.last();
+  custom_knots.reverse();
+  for (float &knot_value : custom_knots) {
+    knot_value = last - knot_value;
+  }
+}
+
 template<typename T>
 static void reverse_curve_point_data(const CurvesGeometry &curves,
                                      const IndexMask &curve_selection,
@@ -1651,6 +1659,17 @@ void CurvesGeometry::reverse_curves(const IndexMask &curves_to_reverse)
     return;
   });
 
+  if (this->nurbs_has_custom_knots()) {
+    const OffsetIndices custom_knots_by_curve = this->nurbs_custom_knots_by_curve();
+    MutableSpan<float> custom_knots = this->nurbs_custom_knots_for_write();
+    curves_to_reverse.foreach_index(GrainSize(256), [&](const int64_t curve) {
+      const IndexRange curve_knots = custom_knots_by_curve[curve];
+      if (!custom_knots.is_empty()) {
+        reverse_custom_knots(custom_knots.slice(curve_knots));
+      }
+    });
+  }
+
   /* In order to maintain the shape of Bezier curves, handle attributes must reverse, but also the
    * values for the left and right must swap. Use a utility to swap and reverse at the same time,
    * to avoid loading the attribute twice. Generally we can expect the right layer to exist when
diff --git a/source/blender/blenkernel/intern/curves_utils.cc b/source/blender/blenkernel/intern/curves_utils.cc
index d6ef3ebc621..dd03af66cb7 100644
--- a/source/blender/blenkernel/intern/curves_utils.cc
+++ b/source/blender/blenkernel/intern/curves_utils.cc
@@ -9,6 +9,8 @@
 #include "BKE_curves_utils.hh"
 #include "BKE_customdata.hh"
 
+#include "BLI_array_utils.hh"
+
 namespace blender::bke::curves {
 
 IndexMask curve_to_point_selection(OffsetIndices<int> points_by_curve,
@@ -214,4 +216,63 @@ void write_all_positions(bke::CurvesGeometry &curves,
 
 }  // namespace bezier
 
+namespace nurbs {
+
+void gather_custom_knots(const bke::CurvesGeometry &src,
+                         const IndexMask &src_curves,
+                         const int dst_curve_offset,
+                         bke::CurvesGeometry &dst)
+{
+  const OffsetIndices<int> src_knots_by_curve = src.nurbs_custom_knots_by_curve();
+  const int start_offset = dst.nurbs_custom_knots_by_curve()[dst_curve_offset].start();
+  Array<int> dst_offsets(src_curves.size() + 1);
+
+  offset_indices::gather_selected_offsets(
+      src_knots_by_curve, src_curves, start_offset, dst_offsets);
+
+  array_utils::gather_group_to_group(src_knots_by_curve,
+                                     dst_offsets.as_span(),
+                                     src_curves,
+                                     src.nurbs_custom_knots(),
+                                     dst.nurbs_custom_knots_for_write());
+}
+
+void update_custom_knot_modes(const IndexMask &mask,
+                              const KnotsMode mode_for_regular,
+                              const KnotsMode mode_for_cyclic,
+                              bke::CurvesGeometry &curves)
+{
+  const VArray<bool> cyclic = curves.cyclic();
+  MutableSpan<int8_t> knot_modes = curves.nurbs_knots_modes_for_write();
+  mask.foreach_index(GrainSize(512), [&](const int64_t curve) {
+    int8_t &knot_mode = knot_modes[curve];
+    if (knot_mode == NURBS_KNOT_MODE_CUSTOM) {
+      knot_mode = cyclic[curve] ? mode_for_cyclic : mode_for_regular;
+    }
+  });
+  curves.nurbs_custom_knots_update_size();
+}
+
+void copy_custom_knots(const bke::CurvesGeometry &src_curves,
+                       const IndexMask &exclude_curves,
+                       bke::CurvesGeometry &dst_curves)
+{
+  BLI_assert(src_curves.curves_num() == dst_curves.curves_num());
+
+  if (src_curves.nurbs_has_custom_knots()) {
+    /* Ensure excluded curves don't have NURBS_KNOT_MODE_CUSTOM set. */
+    bke::curves::nurbs::update_custom_knot_modes(
+        exclude_curves, NURBS_KNOT_MODE_NORMAL, NURBS_KNOT_MODE_NORMAL, dst_curves);
+    IndexMaskMemory memory;
+    bke::curves::nurbs::gather_custom_knots(
+        src_curves,
+        IndexMask::from_difference(
+            src_curves.nurbs_custom_knot_curves(memory), exclude_curves, memory),
+        0,
+        dst_curves);
+  }
+}
+
+}  // namespace nurbs
+
 }  // namespace blender::bke::curves
diff --git a/source/blender/blenloader/intern/versioning_450.cc b/source/blender/blenloader/intern/versioning_450.cc
index 7ba0ed7d857..e5b87403e2a 100644
--- a/source/blender/blenloader/intern/versioning_450.cc
+++ b/source/blender/blenloader/intern/versioning_450.cc
@@ -29,7 +29,10 @@
 #include "BKE_anim_data.hh"
 #include "BKE_animsys.h"
 #include "BKE_armature.hh"
+#include "BKE_curves.hh"
+#include "BKE_customdata.hh"
 #include "BKE_fcurve.hh"
+#include "BKE_grease_pencil.hh"
 #include "BKE_main.hh"
 #include "BKE_mesh_legacy_convert.hh"
 #include "BKE_node.hh"
@@ -68,6 +71,49 @@ static void version_fix_fcurve_noise_offset(FCurve &fcurve)
   }
 }
 
+/**
+ * Fixes situation when `CurvesGeometry` instance has curves with `NURBS_KNOT_MODE_CUSTOM`, but has
+ * no custom knots.
+ */
+static void fix_curve_nurbs_knot_mode_custom(Main *bmain)
+{
+  auto fix_curves = [](blender::bke::CurvesGeometry &curves) {
+    if (curves.custom_knots != nullptr) {
+      return;
+    }
+
+    int8_t *knot_modes = static_cast<int8_t *>(CustomData_get_layer_named_for_write(
+        &curves.curve_data, CD_PROP_INT8, "knots_mode", curves.curve_num));
+    if (knot_modes == nullptr) {
+      return;
+    }
+
+    for (const int curve : curves.curves_range()) {
+      int8_t &knot_mode = knot_modes[curve];
+      if (knot_mode == NURBS_KNOT_MODE_CUSTOM) {
+        knot_mode = NURBS_KNOT_MODE_NORMAL;
+      }
+    }
+    curves.nurbs_custom_knots_update_size();
+  };
+
+  LISTBASE_FOREACH (Curves *, curves_id, &bmain->hair_curves) {
+    blender::bke::CurvesGeometry &curves = curves_id->geometry.wrap();
+    fix_curves(curves);
+  }
+
+  LISTBASE_FOREACH (GreasePencil *, grease_pencil, &bmain->grease_pencils) {
+    for (GreasePencilDrawingBase *base : grease_pencil->drawings()) {
+      if (base->type != GP_DRAWING) {
+        continue;
+      }
+      blender::bke::greasepencil::Drawing &drawing =
+          reinterpret_cast<GreasePencilDrawing *>(base)->wrap();
+      fix_curves(drawing.strokes_for_write());
+    }
+  }
+}
+
 static void nlastrips_apply_fcurve_versioning(ListBase &strips)
 {
   LISTBASE_FOREACH (NlaStrip *, strip, &strips) {
@@ -6184,6 +6230,10 @@ void blo_do_versions_450(FileData * /*fd*/, Library * /*lib*/, Main *bmain)
     FOREACH_NODETREE_END;
   }
 
+  if (!MAIN_VERSION_FILE_ATLEAST(bmain, 405, 86)) {
+    fix_curve_nurbs_knot_mode_custom(bmain);
+  }
+
   /* Always run this versioning (keep at the bottom of the function). Meshes are written with the
    * legacy format which always needs to be converted to the new format on file load. To be moved
    * to a subversion check in 5.0. */
diff --git a/source/blender/editors/curves/intern/curves_edit.cc b/source/blender/editors/curves/intern/curves_edit.cc
index 02117e24130..9dfe1974dca 100644
--- a/source/blender/editors/curves/intern/curves_edit.cc
+++ b/source/blender/editors/curves/intern/curves_edit.cc
@@ -106,6 +106,7 @@ static void append_point_knots(const Span<IndexRange> src_ranges,
   for (const int appended_curve : dst_to_src_curve.index_range()) {
     const int dst_curve = appended_curve + old_curves_num;
     if (knot_modes[dst_curve] != NURBS_KNOT_MODE_CUSTOM) {
+      range++;
       continue;
     }
     const int src_curve = dst_to_src_curve[appended_curve];
@@ -244,12 +245,7 @@ static void append_curve_knots(const IndexMask &mask, bke::CurvesGeometry &curve
 {
   curves.nurbs_custom_knots_update_size();
   const int old_curves_num = curves.curves_num() - mask.size();
-  const OffsetIndices<int> knots_by_curve = curves.nurbs_custom_knots_by_curve();
-  MutableSpan<float> knots = curves.nurbs_custom_knots_for_write();
-  mask.foreach_index(GrainSize(512), [&](const int src_curve, const int appended_curve) {
-    const int dst_curve = old_curves_num + appended_curve;
-    knots.slice(knots_by_curve[dst_curve]).copy_from(knots.slice(knots_by_curve[src_curve]));
-  });
+  bke::curves::nurbs::gather_custom_knots(curves, mask, old_curves_num, curves);
 }
 
 void duplicate_curves(bke::CurvesGeometry &curves, const IndexMask &mask)
@@ -703,6 +699,10 @@ void resize_curves(bke::CurvesGeometry &curves,
   });
 
   dst_curves.update_curve_types();
+  if (dst_curves.nurbs_has_custom_knots()) {
+    bke::curves::nurbs::update_custom_knot_modes(
+        dst_curves.curves_range(), NURBS_KNOT_MODE_NORMAL, NURBS_KNOT_MODE_NORMAL, dst_curves);
+  }
 
   /* Move the result into `curves`. */
   curves = std::move(dst_curves);
diff --git a/source/blender/editors/grease_pencil/intern/grease_pencil_edit.cc b/source/blender/editors/grease_pencil/intern/grease_pencil_edit.cc
index 1bf2e056cc2..0cfdeb86cb2 100644
--- a/source/blender/editors/grease_pencil/intern/grease_pencil_edit.cc
+++ b/source/blender/editors/grease_pencil/intern/grease_pencil_edit.cc
@@ -1217,6 +1217,11 @@ static bke::CurvesGeometry set_start_point(const bke::CurvesGeometry &curves,
                     dst_attributes);
 
   dst_curves.update_curve_types();
+  /* TODO: change to copying knots by point. */
+  if (curves.nurbs_has_custom_knots()) {
+    bke::curves::nurbs::update_custom_knot_modes(
+        dst_curves.curves_range(), NURBS_KNOT_MODE_NORMAL, NURBS_KNOT_MODE_NORMAL, dst_curves);
+  }
   return dst_curves;
 }
 
@@ -3066,6 +3071,24 @@ static bke::CurvesGeometry extrude_grease_pencil_curves(const bke::CurvesGeometr
                          dst_attributes);
 
   dst.update_curve_types();
+  if (src.nurbs_has_custom_knots()) {
+    IndexMaskMemory memory;
+    const VArray<int8_t> curve_types = src.curve_types();
+    const VArray<int8_t> knot_modes = dst.nurbs_knots_modes();
+    const OffsetIndices<int> dst_points_by_curve = dst.points_by_curve();
+    const IndexMask include_curves = IndexMask::from_predicate(
+        src.curves_range(), GrainSize(512), memory, [&](const int64_t curve_index) {
+          return curve_types[curve_index] == CURVE_TYPE_NURBS &&
+                 knot_modes[curve_index] == NURBS_KNOT_MODE_CUSTOM &&
+                 points_by_curve[curve_index].size() == dst_points_by_curve[curve_index].size();
+        });
+    bke::curves::nurbs::update_custom_knot_modes(
+        include_curves.complement(dst.curves_range(), memory),
+        NURBS_KNOT_MODE_ENDPOINT,
+        NURBS_KNOT_MODE_NORMAL,
+        dst);
+    bke::curves::nurbs::gather_custom_knots(src, include_curves, 0, dst);
+  }
   return dst;
 }
 
diff --git a/source/blender/editors/grease_pencil/intern/grease_pencil_geom.cc b/source/blender/editors/grease_pencil/intern/grease_pencil_geom.cc
index 3277a8e7340..aab3a46e5d6 100644
--- a/source/blender/editors/grease_pencil/intern/grease_pencil_geom.cc
+++ b/source/blender/editors/grease_pencil/intern/grease_pencil_geom.cc
@@ -341,6 +341,10 @@ blender::bke::CurvesGeometry curves_merge_by_distance(const bke::CurvesGeometry
     });
   });
 
+  if (dst_curves.nurbs_has_custom_knots()) {
+    bke::curves::nurbs::update_custom_knot_modes(
+        dst_curves.curves_range(), NURBS_KNOT_MODE_NORMAL, NURBS_KNOT_MODE_NORMAL, dst_curves);
+  }
   return dst_curves;
 }
 
diff --git a/source/blender/geometry/intern/curves_remove_and_split.cc b/source/blender/geometry/intern/curves_remove_and_split.cc
index fb51095aa71..75b5413c4a0 100644
--- a/source/blender/geometry/intern/curves_remove_and_split.cc
+++ b/source/blender/geometry/intern/curves_remove_and_split.cc
@@ -6,6 +6,7 @@
 
 #include "BKE_attribute.hh"
 #include "BKE_curves.hh"
+#include "BKE_curves_utils.hh"
 #include "BKE_deform.hh"
 
 #include "GEO_curves_remove_and_split.hh"
@@ -109,6 +110,10 @@ bke::CurvesGeometry remove_points_and_split(const bke::CurvesGeometry &curves,
   dst_curves.update_curve_types();
   dst_curves.remove_attributes_based_on_types();
 
+  if (curves.nurbs_has_custom_knots()) {
+    bke::curves::nurbs::update_custom_knot_modes(
+        dst_curves.curves_range(), NURBS_KNOT_MODE_NORMAL, NURBS_KNOT_MODE_NORMAL, dst_curves);
+  }
   return dst_curves;
 }
 
diff --git a/source/blender/geometry/intern/extend_curves.cc b/source/blender/geometry/intern/extend_curves.cc
index 4a2efc8d443..c3bc7fbc0a2 100644
--- a/source/blender/geometry/intern/extend_curves.cc
+++ b/source/blender/geometry/intern/extend_curves.cc
@@ -360,7 +360,10 @@ bke::CurvesGeometry extend_curves(bke::CurvesGeometry &src_curves,
       }
     }
   });
-
+  if (src_curves.nurbs_has_custom_knots()) {
+    bke::curves::nurbs::update_custom_knot_modes(
+        dst_curves.curves_range(), NURBS_KNOT_MODE_NORMAL, NURBS_KNOT_MODE_NORMAL, dst_curves);
+  }
   return dst_curves;
 }
 
diff --git a/source/blender/geometry/intern/fillet_curves.cc b/source/blender/geometry/intern/fillet_curves.cc
index 95c058a3974..e532b90e2ca 100644
--- a/source/blender/geometry/intern/fillet_curves.cc
+++ b/source/blender/geometry/intern/fillet_curves.cc
@@ -516,7 +516,10 @@ static bke::CurvesGeometry fillet_curves(const bke::CurvesGeometry &src_curves,
                                       dst_points_by_curve,
                                       unselected,
                                       dst_attributes);
-
+  if (src_curves.nurbs_has_custom_knots()) {
+    bke::curves::nurbs::update_custom_knot_modes(
+        dst_curves.curves_range(), NURBS_KNOT_MODE_NORMAL, NURBS_KNOT_MODE_NORMAL, dst_curves);
+  }
   return dst_curves;
 }
 
diff --git a/source/blender/geometry/intern/merge_curves.cc b/source/blender/geometry/intern/merge_curves.cc
index a1d5936f9fb..1e0bec6a5de 100644
--- a/source/blender/geometry/intern/merge_curves.cc
+++ b/source/blender/geometry/intern/merge_curves.cc
@@ -5,6 +5,7 @@
 #include "BLI_array_utils.hh"
 #include "BLI_stack.hh"
 
+#include "BKE_curves_utils.hh"
 #include "BKE_deform.hh"
 
 #include "GEO_merge_curves.hh"
@@ -305,6 +306,16 @@ bke::CurvesGeometry curves_merge_endpoints(const bke::CurvesGeometry &src_curves
   bke::CurvesGeometry merged_curves = join_curves_ranges(ordered_curves, joined_curves_by_new);
   merged_curves.cyclic_for_write().copy_from(cyclic);
 
+  /**
+   * `curves_merge_endpoints` seems to be working only with CURVE_TYPE_POLY, still adding this here
+   * in advance.
+   */
+  if (src_curves.nurbs_has_custom_knots()) {
+    bke::curves::nurbs::update_custom_knot_modes(merged_curves.curves_range(),
+                                                 NURBS_KNOT_MODE_NORMAL,
+                                                 NURBS_KNOT_MODE_NORMAL,
+                                                 merged_curves);
+  }
   return merged_curves;
 }
 
diff --git a/source/blender/geometry/intern/reorder.cc b/source/blender/geometry/intern/reorder.cc
index 559bf75d106..88c4900060a 100644
--- a/source/blender/geometry/intern/reorder.cc
+++ b/source/blender/geometry/intern/reorder.cc
@@ -6,6 +6,7 @@
 #include "BKE_attribute_filters.hh"
 #include "BKE_attribute_math.hh"
 #include "BKE_curves.hh"
+#include "BKE_curves_utils.hh"
 #include "BKE_deform.hh"
 #include "BKE_geometry_set.hh"
 #include "BKE_instances.hh"
@@ -291,6 +292,12 @@ static void copy_and_reorder_curves(const bke::CurvesGeometry &src_curves,
                                     attribute_filter,
                                     dst_curves.attributes_for_write());
   dst_curves.tag_topology_changed();
+  if (src_curves.nurbs_has_custom_knots()) {
+    dst_curves.nurbs_custom_knots_update_size();
+    IndexMaskMemory memory;
+    bke::curves::nurbs::gather_custom_knots(
+        src_curves, IndexMask::from_indices(old_by_new_map, memory), 0, dst_curves);
+  }
 }
 
 static void copy_and_reorder_instaces(const bke::Instances &src_instances,
diff --git a/source/blender/geometry/intern/resample_curves.cc b/source/blender/geometry/intern/resample_curves.cc
index ad87163debf..a2fd28deade 100644
--- a/source/blender/geometry/intern/resample_curves.cc
+++ b/source/blender/geometry/intern/resample_curves.cc
@@ -441,6 +441,7 @@ static CurvesGeometry resample_to_uniform(const CurvesGeometry &src_curves,
 
   resample_to_uniform(src_curves, selection, output_ids, dst_curves);
 
+  bke::curves::nurbs::copy_custom_knots(src_curves, selection, dst_curves);
   return dst_curves;
 }
 
@@ -475,6 +476,7 @@ CurvesGeometry resample_to_count(const CurvesGeometry &src_curves,
 
   resample_to_uniform(src_curves, selection, output_ids, dst_curves);
 
+  bke::curves::nurbs::copy_custom_knots(src_curves, selection, dst_curves);
   return dst_curves;
 }
 
@@ -526,6 +528,7 @@ CurvesGeometry resample_to_length(const CurvesGeometry &src_curves,
 
   resample_to_uniform(src_curves, selection, output_ids, dst_curves);
 
+  bke::curves::nurbs::copy_custom_knots(src_curves, selection, dst_curves);
   return dst_curves;
 }
 
@@ -622,6 +625,7 @@ CurvesGeometry resample_to_evaluated(const CurvesGeometry &src_curves,
     attribute.finish();
   }
 
+  bke::curves::nurbs::copy_custom_knots(src_curves, selection, dst_curves);
   return dst_curves;
 }
 
diff --git a/source/blender/geometry/intern/set_curve_type.cc b/source/blender/geometry/intern/set_curve_type.cc
index a401e50afd8..43698082de9 100644
--- a/source/blender/geometry/intern/set_curve_type.cc
+++ b/source/blender/geometry/intern/set_curve_type.cc
@@ -450,7 +450,7 @@ static bke::CurvesGeometry convert_curves_to_bezier(const bke::CurvesGeometry &s
 
     attribute.dst.finish();
   }
-
+  bke::curves::nurbs::copy_custom_knots(src_curves, selection, dst_curves);
   return dst_curves;
 }
 
@@ -623,7 +623,7 @@ static bke::CurvesGeometry convert_curves_to_nurbs(const bke::CurvesGeometry &sr
 
     attribute.dst.finish();
   }
-
+  bke::curves::nurbs::copy_custom_knots(src_curves, IndexMask(), dst_curves);
   return dst_curves;
 }
 
@@ -754,7 +754,7 @@ static bke::CurvesGeometry convert_curves_to_catmull_rom_or_poly(
 
     attribute.dst.finish();
   }
-
+  bke::curves::nurbs::copy_custom_knots(src_curves, selection, dst_curves);
   return dst_curves;
 }
 
diff --git a/source/blender/geometry/intern/subdivide_curves.cc b/source/blender/geometry/intern/subdivide_curves.cc
index d14a3c34f15..3442dc58739 100644
--- a/source/blender/geometry/intern/subdivide_curves.cc
+++ b/source/blender/geometry/intern/subdivide_curves.cc
@@ -419,6 +419,7 @@ bke::CurvesGeometry subdivide_curves(const bke::CurvesGeometry &src_curves,
     attribute.dst.finish();
   }
 
+  bke::curves::nurbs::copy_custom_knots(src_curves, selection, dst_curves);
   return dst_curves;
 }
 
diff --git a/source/blender/geometry/intern/trim_curves.cc b/source/blender/geometry/intern/trim_curves.cc
index c7dfdce85ae..381d2610450 100644
--- a/source/blender/geometry/intern/trim_curves.cc
+++ b/source/blender/geometry/intern/trim_curves.cc
@@ -1070,6 +1070,10 @@ bke::CurvesGeometry trim_curves(const bke::CurvesGeometry &src_curves,
 
   dst_curves.remove_attributes_based_on_types();
   dst_curves.tag_topology_changed();
+  if (src_curves.nurbs_has_custom_knots()) {
+    bke::curves::nurbs::update_custom_knot_modes(
+        dst_curves.curves_range(), NURBS_KNOT_MODE_NORMAL, NURBS_KNOT_MODE_NORMAL, dst_curves);
+  }
   return dst_curves;
 }
 
diff --git a/source/blender/io/usd/intern/usd_writer_curves.cc b/source/blender/io/usd/intern/usd_writer_curves.cc
index bbb34a4e6c4..340dc170939 100644
--- a/source/blender/io/usd/intern/usd_writer_curves.cc
+++ b/source/blender/io/usd/intern/usd_writer_curves.cc
@@ -304,14 +304,13 @@ static void populate_curve_props_for_nurbs(const bke::CurvesGeometry &curves,
 
     const int knots_num = bke::curves::nurbs::knots_num(tot_points, order, is_cyclic);
     Array<float> temp_knots(knots_num);
-
-    if (mode == NURBS_KNOT_MODE_CUSTOM) {
-      bke::curves::nurbs::copy_custom_knots(
-          order, is_cyclic, custom_knots.slice(custom_knots_by_curve[i_curve]), temp_knots);
-    }
-    else {
-      bke::curves::nurbs::calculate_knots(tot_points, mode, order, is_cyclic, temp_knots);
-    }
+    bke::curves::nurbs::load_curve_knots(mode,
+                                         tot_points,
+                                         order,
+                                         is_cyclic,
+                                         custom_knots_by_curve[i_curve],
+                                         custom_knots,
+                                         temp_knots);
 
     /* Knots should be the concatenation of all batched curves.
      * https://graphics.pixar.com/usd/dev/api/class_usd_geom_nurbs_curves.html#details */