It appears that when clicking on a chord symbol that was entered locally (using Opt-L on the Mac), the popover does not populate with the existing chord symbol, whereas it does for chord symbols entered globally.
It would be a very helpful quality-of-life improvement if clicking on any chord symbol, whether entered locally or globally, populated the popover with the existing symbol, making it much quicker to edit.
I tried to reproduce it, but it’s working here on a Mac. (I don’t have a midi controller, so I entered the chords with the regular keyboard, but that shouldn’t matter?)
Many thanks for your detective work @FredGUnn. I can confirm that I see the same behaviour: there are no issues with single-staff instruments, but the problem is easily reproducible with grand staff instruments.
I have my fingers crossed that this might be addressed in a future update, as it seems that at present the only way to update a chord symbol in these circumstances is to delete it and enter it again.