Each arrangement, note or curve sequence has its own undo history. Although you edit the curve sequence using the mixer sliders in the arrangement editor, it is still modifying events in the curve sequence. If there is no curve sequence allocated on the track, then the creation of a curve sequence event is stored in the arrangement edit history.
A solution could be; When you edit curves with sliders in the mixer, a sort of curve edit reference would be added to the arrangement undo history, so that mixer slider changes can be undone in the arrangement editor. I’ll consider this at some point.
Instead of opening the curve editor to undo, you can alternatively use the shortcut menu ‘Undo inside’ on the curve sequence event.
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