I have a new cycleops fluid turbo trainer with the yellow clutch knob for the roller adjustment.

I like to leave a spare bike setup ready for quick adhoc sessions, but this model doesn’t seem to have any sort of quick release.

Seems to leave a nice dent in the tyre ?

It will be fine, the impression in the tyre will soon disappear when you start riding. I have had the same set up for the past few years and the bike has only been taken off a handful of times.

I leave mine attached to the trainer but adjust the roller so that it’s not pressing on the tyre when not in use.

This was easier with the older version but if i was doing it with the new version I would put a small pen mark on the dial and wind it back by however many revolutions is need to release the pressure (imagine it’s 5 full rotations). Then when you come to use it just wind it in by 5 and you’re back where you started. Not quite quick release but quicker enough to be viable.