In general I'd like to get an Undo/Redo List with much more abilities. It would be great when all steps that are changing values (concerning sound) could be implemented.
Often in a process there are for example only two steps to be corrected and these two steps should be selectable from a list by random access. Therefore, the serial way of working on Undo/Redo should be changed into random access.
Let me suggest the following:
1) The Undo/Redo list is saved/opend with the session so that no changes get lost and the number of steps is not limited (cleaning up by user could be allowed, too).
2) The entries are sorted by date worked on the session (or freely selectable criterias such as Track, Volume, Pan, Plugin etc.)
3) When pressing OPTION/CTRL+Z a pop-up window shows the scrollable Undo/Redo list. An entry can be selected by mouse click. Then choosing (U)ndo or (R)edo starts the action described. The latest action instead could be undone and redone by a keyboard short cut, so that no mouse action is needed.
4) The action is labeled clearly and precisely.
Date, Time, Track, Plug-In, Event, Value Change (U)ndo (R)edo
xx/yy/zz, 03:15, Git1, none, Vol, +3.4dB, (U)ndo (R)edo
xx/yy/zz, 06:22, Tom1, none, Pan, L+30, (U)ndo (R)edo
xx/yy/zz, 05:24, Kick, Compressor XY, Thresh, -3dB, (U)ndo (R)edo
xx/yy/zz, 08:01, Voc1, none, move volume automation -2.1dB, (U)ndo (R)edo
xx/yy/zz, 08:01, Voc2, none, volume automation new point +2.8dB, (U)ndo (R)edo
When for example 'Git1' is clicked all changes on this track are shown (maybe in a separate window?). (U)ndo and (R)edo can be clicked to execute the action.
5) Even the configuration of OPTION/CTRL+Z should be possible to be set to (D)irect Action (as so far) and (S)how List To Choose From in the PT operation preferences.
6) All sorts of other actions like switching, zooming and so on naturally are NOT a part of the improvements but only changes that affect the sound of a track.
This is only a raw suggestion and certainly can be improved much more or in a different way.