I did a quick search of the forum for this idea but couldn't find anything resembling it.
I wonder if it was possible to select an item in the history dialog, then only edit that particular item from the project.
I was recently editing a MIDI track and realised that there was a section that I'd altered quite a few steps back. I wanted to undo that particular edit without undoing the edits after this one. How difficult would it be to reach into the History and selectively undo something?

I have often wanted to do this also. But realized it couldn't be done.

I wonder it could be a source of total mockups.
Some things really depend on each other.
 
If you split a clip, then delete one part, and then go back to undo split only - what happends?
things like that...