Hello Andrew and Mike,
I did a new test, I created a new user session on my Mac. I opened a file with melody already made on the old session, and there, miracle, the Lead Sheet Window works perfectly with Jazz Fonts!!! Yet I had reinstalled BIAB without success.
I suppose I'll have to delete a preference file somewhere, but I can't see which one, I'd already tried that, without success either!
But it's already a good way forward!


French jazz musician - Double Bass, baritone guitar, arrangements
Work on MacBook Pro 16" M1Pro macOs Monterey 12.6
Logic Pro X, Musescore, BIAB, Final Cut X