First cut all objects on the same layer, then repeat

No, it’s not possible at this time. Part of the trouble is that there’s nothing that says you have to cut all the shapes on a layer at the same time, and in fact you often don’t want to.

Making the system able to handle cutting everything on a single layer, then returning to the first for the next pass is possible, but honestly quite hard to insert into the current way things are ordered.

I would suggest adding a small air assist jet to your setup - even a little air blown directly into the cut will reduce charring, and will produce deeper and cleaner cuts with fewer passes.