Hi everybody,
I think I just found a solution (workaround) to the problem (using grace notes simultaneously before AND after barline in different players). It doesn’t need to invoke hidden tuplets. It uses just “duplicates” and “hidden note heads and stems”. (Eventually suppress playback for the hidden elements and tweaking in key editor is desired, if right playback is needed.)
I attach an explanatory picture and the Dorico file. I hope it can help. Greetings.
grace notes before AND after barline.dorico (518.0 KB)