You need that button to trace, overlap or broadcast. For example: when the character walks into the volume you can bind the turn off event to the accion even (pressi g ‘I’ or every time player presses the key, have it check for overlapping actors with valid interface.
Maybe store a reference to the light turned on most recently “recentLight” and when 1 is pressed check the reference to “recentLight”. If its null do nothing or if its pointing to a light actor, run the event to switch of said light.