As things currently stand, you have the ability to include a KML layer with your map… but there is no communication between the map, the KML layer, and the app - the app will have no idea that a pin is inside a KML layer boundary.
As @tsuji_koichi mentioned, you could build out the functionality to establish your KML layers inside of your app sheet app… But I’ve yet to see anybody build something like this and get it to 100% work.
A few months ago I had a client that wanted this exact ability; we were building a field inspection app, and he wanted the app to automatically know where somebody was based on KML layers.
But since there’s no communication between the KML layer and the app, that functionality wasn’t possible.
In an effort to solve this problem, I built a sample app to try and figure out a way to get all of this to work inside of an app - But I could never get it to work with irregular shapes.
It works with a perfect box, a rectangular shape… But if you have any kind of irregularity to your shapes, we need to come up with some other way to determine if you’re inside that space.