Bonzai7

Pressing and holding a parameter such as amp drive will change the screen to Parameter and Controller. When a footswitch is selected as Controller a second page becomes available with Snapshot Control (On/Off). I think this is the behavior you are looking for.

From page 37 of the manual: Bias "Changes the Bias of the power tubes. Lower values achieve a “cold" Class AB biasing. At maximum, the amp is operating in Class A." I believe operating at Class A is pretty much the opposite of raising the bias on a Class AB amp. The elimination of the crossover in a Class A amp s generally thought to make for a sweeter clean sound. In the real world a class A Marshall Super Lead is impossible, but we're not in Kansas anymore are we.