Well I was curious on that point. So with 4S6 I didn’t add a runway - literally just 2 GA parking docks. I wanted to see what you woould be presented with in the world map and I had both the runway start points and the parking spots to choose from. This makes the whole process for a bush strip much easier. As for taxiways - those don’t link to the runway per se, they link to a hold-short, so I think you could build them in you mod and it will still work.
I’ve yet to find a good resource explaining exactly how this aspect of scenery building works, but it works!
(My problem with ADE is even more basic - it cant find my package folders. I think I need to run the extra mod they released, but when I saw how easy it was to do in the SDK, I was like, why bother…?)