I read somewhere (I think GitHub Source Code) that App Inventor can get XML files or something alike from the .aar when creating an extension if you import it with the .jar? When I did this and tried creating the view, I get: "Failed resolution of: .../R$dimen"
#1. Your topic is closed, I can't ask anything if I had any questions. #2. Your topic does not answer my question, although it it related through aars and jars, it just teaches you how to import both file types.
For anyone who is wondering why this isn't possible...