You may not need playing techniques and playback techniques for combinations of stops, because again, they can stack. I would probably just do them for the individual stops instead of combinations. The only case in which you might do a special playback technique that triggers multiple stops is if the organ has certain “presets” where with one button / keyswitch you can change many stops at once. In that case I would probably create playback techniques for these various presets.
If you don’t want multiple lines of labels in the score for the stops being triggered, you can hide some of them.
BTW I just remembered another user previously made a Dorico map for Organteq: Organteq with Dorico
It is not the same organ but their map gives individual control over stops. It is the only example I can think of in Dorico where someone has made an expression map with full stop controls for an organ - being able to turn any stops on or off. You can look at what was done in that as an example potentially. See the later post in the thread (Dec 2023) for the updated Dorico 5 version of his map.