Maybe, even better: The ability to filter the undo history by type of actions. So you could colour all "selection" actions yellow, "transport" actions blue and whatnot. And maybe decide to have certain types hidden.
This way you could have them all visible but could find that important red item (or whatever) quickly amongst all those green ones. Or have the green ones not show at all.
And, because it's reaper: All the colours are configurable, of course