Draft: Symbol Editor: Update New Symbol and Derive from Existing Symbol dialog.
Currently Derive from Existing Symbol dialog shows an infobar that doesn't update as (i think) it should, it doesn't update at all if i am not mistaken and this may be misleading when the dropdown list changes by accident.
Proposed patch, while not the best that can happen, seems to be good enough and work as expected.
(infobar is not really consistent when the original selection comes from a parent VS a derived symbol, but it sure is a slightly improvement of the current status, since it informs about what is going to happen, and also auto updates some other fields in the same dialog.)
It needs some small further cleanup before considered ready to merge, but i would like to ask for some feedback/help based on the preview video and the small inconsistency i described some lines above.
MR preview: