Animation: Blend Offset Slider

Adds an operator to the Graph Editor that moves the selected
segment up/down so it aligns with the keys before/after the segment.

Co-authored-by: Ares Deveaux <aresdevo@gmail.com>
Co-authored-by: Sybren A. Stüvel <sybren@blender.org>
Pull Request: https://projects.blender.org/blender/blender/pulls/110544

scripts/startup/bl_ui/space_graph.py

@@ -299,6 +299,7 @@ class GRAPH_MT_key_blending(Menu):
         layout.operator("graph.blend_to_neighbor", text="Blend to Neighbor")
         layout.operator("graph.blend_to_default", text="Blend to Default Value")
         layout.operator("graph.ease", text="Ease")
+        layout.operator("graph.blend_offset", text="Blend Offset")
 
 
 class GRAPH_MT_key_smoothing(Menu):