Return to dock possible for vacuums?

I saw in the documentation, that it is possible to use vacuums with google assistant. But I only saw that thw switch has the ga=Vacuum tag. So I guess it is to start / stop the vacuum.

Is it also already implemented to say: “Return to dock” or something similar with openhab?

Not sure if they works straight away, but would be nice if it would.

A workaround could be to define an on/off switch named dock or something, pipe it into Google assistant and create a rule that when activated the vacuum should go back to the dock.

No. So far the Vacuum is only available as a single switch. You may add your feature request to the project at Issues · openhab/openhab-google-assistant · GitHub