So, when I was creating my map, I got confused because I couldn't link a sensor with a gate that I was trying to put together. Then I realized it's because that part of the map was in a different map section. My suggestion is to make it so that you can actually put together two map sections with sensor links.

For example, I wanted to have a set of switches that the player had no idea what they did until the very end of the map -- several screens later.