The BOSS GX-100 provides two ways to assign functions to the number switches, footswitches, and expression pedal.
CONTROL FUNCTION assigns system parameters to the top panel footswitches, the expression pedal (EXP1), and the expression pedal or footswitch connected to the CTL 3, 4/EXP 2 jack. Refer to "CONTROL FUNCTION" in the GX-100 Parameter Guide for the full list of assignable functions.
ASSIGN SETTING allows detailed configuration of which controller controls which parameter, with up to 20 assignments available per memory. Refer to "TARGET list" in the GX-100 Parameter Guide for the full list of assignable parameters.