If you only want a specific group to be able to toggle NPCs on/off, add this to your server.cfg:
add_ace group.admin "NoNPC.Toggle" allow
Replace "group.admin" with whatever you want.
If you want anyone to be able to toggle NPCs, add this instead:
add_ace builtin.everyone "NoNPC.Toggle" allow
Press the key to the right of the "0" on your number row (not numpad). On US keyboards it's "-", on Scandinavian keyboards it's "+".
It's mapped to the INPUT_VEH_PREV_RADIO_TRACK function.
