Heres a little drawing of what I would hope the result to look like.
I think a good solution from a usability perspective would be to not only allow stacking to be turned on or off (or 100%) but allow to assign stacking groups to queries.
So in this example I would assign Netzbezug and PV Produktion to Stacking Group A and Verbrauch and Einspeisung to Stacking Group B and the result would look like this:
