From pg 8, Footswitch Functions Guide:
"EFFECT: CHANNEL INCREMENT/DECREMENT
“Inc / Dec” functions allow you to scroll through channels, stepping up or down .
Increment/Decrement – Designates the step size, whether up or down . For a switch that goes to the next channel, select +1 . For a switch that goes to the previous channel, select -1 .
Wrap – Determines whether the Channel wraps when you reach either end of the list .
Lower Limit, Upper Limit – These set the lowest and highest Channels that can be accessed using the switch, allowing you to restrict the range . If you’re using UP and DOWN channel switches, you’ll probably want to set the same limits for both .
€ The LED ring is bright when the switch is active, otherwise dim ."
For INC you could have one switch that increases +1, and for DEC, a 2nd switch that decreases -1. Bank limits would be 4 with wrap, for A, B, C and D.
Or, you could use 2 switches that toggle between channels A & B, and C & D:
"EFFECT: CHANNEL TOGGLE
“Toggle” functions allow you to switch a specific effect block between two Channels. The Effect parameter selects which effect you want the switch to control . Primary Channel and Secondary Channel set the desired Channels .
€ The LED ring is bright for the Primary channel, dim for the Secondary channel, and OFF if a different channel is selected, or if the effect assigned to the switch is not contained in the current preset ."