Didn't we already have this conversation? You can make an engraver to
do all the French ornaments. The outline is on Scores of Beauty. I can
help you do it if you like. Anything like what you have suggested is a
just a sort of hack. Even though you can force it to work, it is
suboptimal. It can be done nicely. Admittedly doing it the good way is
advanced lilypond, but there are lots of people here with deep skills.
And this thread title is incorrect - we need to start a new distinct
one. It's hijacked another thread (thread hijacking is a common
problem). I'll leave it to you to initiate a new topic thread.
Andrew