I also have TRV from AVM (DECT 301 and Comet).
I came across the following:
Window open, climate off - Blueprints Exchange - Home Assistant Community (home-assistant.io)
This works until the TVR is switched off, after closing the window the TVR goes back to heating mode, so far ok.
ONLY: also for default: Comfort.
I’m failing to rebuild the blueprint, maybe you can do that, or I’ll write something in there