The ability to live without your Realm, living in someone else's

I have a problem living with a friend.

I don't really want to build in Minecraft right now, and I want to live with my friend. He added me as a trusted player, but when he logs out, I can't access his realm. I really want to help him build, but I can't because I can't access his realm. I want them to add the /realm add [Nickname] command so I can live in my friend's realm. ♥️