My understanding (though I can't claim to have tested it myself) is that the SPAWN_EXTERIOR_SECOND can be used with additional exit doors, but this only works (the only way for it to know which door you triggered) with Asobo's (very poorly implemented, in my opinion) new door behaviors, which trigger the automatic entering/exiting of the cockpit. Not only is this restrictive for my aircraft, but I have also received many notes of gratitude for not implementing this system that forces your character out of the airplane when any door is opened. Unfortunately, this has been the case for most MSFS 2024 features. They sound great in theory, but when you see how they were implemented, it leaves you home-brewing your own solution to achieve similar results. That's only my opinion, of course. I'm sure there are developers who are using all the new features exactly as they were intended, but I suspect they would also struggle trying to implement some of the custom features alongside that my aircraft have become known for.