Well that's complicated lol!
I just wanted them to come on and off with the courtesy light lol. Going back to the original question, would that be easy to do? Rather than adding timers and photoelectric sensors? Literally just want the headlights (or parking lights) to mimic the courtesy lights.
Going back to basics: would a 12v feed with a diode from the courtesy lights to the side lights work? So that when the courtesy light turns on, the sidelights turn on, but when the sidelights are manually turned on, it doesn't turn the courtesy lights on.
If that works, that's literally all I originally wanted
the only thing I'd need to know is the wattage of the diode. It would be a 12v diode, but what wattage?