On the glare shield between AP ENG and SPEED
What does it do?
Transfers autopilot control between AP1 & AP2
There is a good series of tutorials that explains everything about the plane:
I can’t remember from the top of my head but I think it was some fuel crossfeed to make sure you have equal amount in both wings.
Oh yes I’ve seen The Dude 
You’re thinking of the manual crossfeed button on the overhead.
OP is referring to this:
From - CRJ-00_and_00-Automatic_Flight_Control_System.pdf (smartcockpit.com)
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