You cannot connect a footswitch and an expression pedal at the same time to the CTL 2,3/EXP 2 jack on the rear panel of the GX-1B.
If you need to use an external footswitch and an expression pedal at the same time, connect one of them to the CTL 2,3/EXP 2 jack using a wired connection, and consider using a Bluetooth-compatible controller (FS-1-WL or EV-1-WL) for the other device.