You should define the ON pin first. For example, output 7 – Bistable relay ON, and output 8 – Bistable relay OFF.
If you defined the “Bistable relay ON” pin only, the firmware will send ON and OFF pulses to one pin. It can be used in some gate control systems to open and close gates when a next signal reverses movement direction.
Zigbee: Look for commands and examples for GPIO outputs. The firmware accepts all commands on the “Bistable relay On” endpoint.