1. If you could click on the Mixer track name then Ctrl+C or Ctrl+X then when you click on the destination track name on the Mixer and Ctrl+V then the dialog (see pic below) will pop up with either Copy or Move set.
Don't know if the copy tracks copies the volume, pan etc.. or VSTs ?
if not that maybe something to look at.

2. So are you talking about clip editing, dragging, fading, volume like Reaper ?

3. With C.u1 if the track in the Mixer had the number in front of it no matter what the name is you can go by the number, so all the dropdown track lists will have a number that you can use for C.1 or C...3,5 rather than C.b,d,g yet still be backward compatible.
Maybe when you select some bars in the chord sheet then in the right click menu you can mute/unmute that section of a track in the track list that will show.
Another is have a snap option in the Audio Edit of 1/4 1/8 1/16 and be able to copy/cut the automation points in the time selection and be able to paste on same track or another track.
All the more reason to show all the tracks in the Audio Edit same as a DAW.

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https://stash.reaper.fm/u/ReaTrak (Scripts for Biab Reaper)
Open SGU in Reaper Instantly