It can be mapped so you press that and another button for various functions, volume control, monitor on and off, safe shutdown, WiFi and bluetooth on or off. It can be skipped and mapped to an existing gpio button so you'd press L plus the buttons for the fiction instead of function plus the buttons for the function.
is it correct, the scriopt only works with GPIO controller wiring? So what to do to get the script running in combination with Arduino based controller pcb?
You wouldn't, the script only looks at the gpio for key presses so you'd have to either use a function button on just the gpio or not use an Arduino if you use this script. That is only if you want the function button, you can do it without a function button I believe