Copying a link from your booklet and assigning a local name is probably the least ugly approach. (It is of course possible that worlds will be renamed, and that there will be more than one world with the same name. So "Dusty Hill" by itself is not a reliable specifier. But you could paste a link and say "I am calling this link dusty_hill for the purposes of this Age's code", and then the name would be associated with the ObjectId.)
I ran into the same problems trying to specify a world for creating linking books. Once I get that sorted out, hopefully, I can make world-communication channels use "the same interface", whatever that means.