I get the concept (pinch small metal ring clamp, slide hose) but it will not move!!!! Anyone have any suggestions? Would like to remove the reservoir so it can be cleaned.

Twist, maybe? I don't use mine and don't remember what that fitting looks like. Also maybe hot water or a hair dryer would loosen it up.
Use some Dow 111 when you do get it apart for next time!!

I removed it at the pump fitting; see the yellow arrow below:

Dans idea is best. Remove the fitting.
Pinching the clip, even putting a pair of gentle pliers on the tubing can damage the tubing or could distort the tension of the clip leading to leaks down the road.

I was under the impression that Dan removed the tube from the fitting? Figured it might be easier to remove it there after seeing the photo (there seems to be an indentation on the metal bit where the clip sits at the connection to the reservoir itself, which makes it difficult to get out of the way). The bit of copper pipe doesn't appear to have the same indentation, so it may be easier to move the clip out of the way and slide the tubing off.

The tubing itself seems relatively robust -- it's certainly not going to slide off (clip or no clip) from the fitting at the reservoir on my machine!

I removed mine recently for cleaning. Just use a needle nose pliers on the clamp and wiggle the hose out. I think it would be hard to damage anything. I originally tried to squeeze the clamp with my fingers--impossible! Rob

Is bleeding of the grouphead required after removing the reservoir for cleaning? I noticed a little air went into the hose when I removed it to clean my reservoir.