Well, I don’t know what to say. I’ve trashed my preferences in both Cubase 9.5.41 and 10.0.20 and still the VST rack instruments “write enable” can not be turned on by a key command (default is Alt/W).
And yes, this ONLY happens with “rack” instruments. I prefer rack instruments mostly because I can save their channel settings in the mixer. Why it works with tracks and not racks is a mystery to me. Another reason I prefer racks is because of this bug: