Copy-paste of keyframes is now slot-aware. See [1] for the design. [1]: https://developer.blender.org/docs/features/animation/tools/action-editor-copy-paste/ In short: - Copy-paste still works broadly as it used to. Only the visible F-Curves are pasted into. - Slot identifiers matter when copying from multiple slots. When copying from one slot, they don't. - Selection of channels (either F-Curves or Slots) determines where keys get pasted into. - Pasting will either copy from the slot with the same identifier (when identifiers matter), or paste whatever was copied (when they do not). - If both F-Curves and slots are selected, only the selected F-Curves get pasted into, and slots without any selected F-Curves are ignored (i.e. target is only defined by selected F-Curves, or only by selected slots, never by a mixture). Fixes #129690 Pull Request: https://projects.blender.org/blender/blender/pulls/133979