Bookmarks are to provide shortcuts to views. You can read about them here:
So they’re not the tool for your task. Presumably you’re playing other things on the endpoint in between the Bach sessions? If not just hit stop and play when you return?
If you are, then what you want is a “saved play state” queue. I don’t think that’s a Roon feature. There is a hacky fix I can think of where you could transfer the queue to an unused endpoint like your phone. You could then transfer it back when you wanted to resume.
I’m just another user BTW, support may have better suggestions when they reply.