I think we can only toggle while the handler is not active.
I toggled to ON and got the script running. But then I couldn't toggle
OFF, presumingly because the script was still running.
By sending it to the background I hope it will allow me to toggle OFF.
I don't know whether this works. On the v4 firmware, we can see files in
/etc/gl-switch.d but I don't know yet how the system determines which
file to choose. I assume it's dependend on the "page" of the display.
But I haven't figured out yet how or rather where those pages are
organised.