Yup, tags are the way to go. A note resides in only one notebook. Doubtful EN will change this any time soon, if ever, as I'd guess it's a major overhaul & (again) tags do pretty much the same thing with the exception of sharing, offline and/or local notebooks. And I'm guessing those exceptions are what they are because of the infrastructure of the database, so again, major overhaul.
You may find this thread helpful, if you've not read it before.