Obviously my answer above still didn’t really answer your question, but it is a better solution (depending what you want to do).
As for adding an ID, follow a similar process. Create a custom actor, but this time make the variable an int (check expose on spawn / instance editable). This way you can assign an ID to each instance in the world.
On the door, the same sort of variable so you can compare if the ID or the trigger matches the ID of the door. The decision then would be how will the door and the trigger validate against themselves. An obvious way would be to use “GetAllActorsOfClass” but I hate using that function for a solution for this sort of mechanic.
If both my replies didn’t help, can you please give a specific example of what you’re trying to do and what objects you have available. Honestly though, direct relationships are the best to work with.
Good luck.
Alex