The schrader valve is to charge the shock with about 150 lbs of nitrogen. DON'T MESS WITH IT.
The rebound adjustment is on the side of the clevis, where the shock connects to the linkage.

Ride on
Brewster

 

Ooops!...now we're talking about the shock...sorry, I was still blathering on about the fork.

C'mon Brewster...this is the second time in a week that I've heard you warn someone about the nitrogen reservoir. Just once...just once, I'd like to hear a horror story...where no one is maimed or killed, of course...where the owner unscrews the schrader valve, and the bike leaps off the garage floor like a Saturn 5 booster rocket...and it's all captured on video.

 

I wish that I had a video of when I disassembled a nitrogen shock that used to be on my Tacoma. I drilled into it to release the nitrogen but hit the fluid section by mistake..........what a mess! The nitrogen was still under pressure when I cut the shock body with a hack saw...........small dent in garage door when things flew apart.

Back to the topic. Releasing the pressure on the bike shock would only create the need to get it recharged in order to regain the shock damping action.

Ride on
Brewster

 

A little OT, but my Race Tech charge recommendation was 175psi for some reason. It's been just about perfect, but I was a little surprised to see it that high over stock.