[Vibraphon]

However, there is more involved. For example, when the user types Abm6/Eb, what he really wants is

Yes, that is what I thought of.
It is not so easy, but I think most could be done using simple rules for positioning and font size.
Attached you find a file, where I tried to define such rules that would work in the most situations.

At the end it is important to get one annotation object for one chord, that could be moved and resized according to the sheet without need to move or resize every single sign in it.

HtH Paul