There should be a way to =add= an event to an existing Part.
Eg. I have an Audio Part with 4 events. This is shared in several places in the song.
I then realise that I want to fix one event in the Part. So I overdub. There should be a way to add the overdub to the existing Part without dissolving it. That way it would auto-magically apply the fix to -all- the shared Parts in the song.