Please for the love of god add this. It's been a request of many users for so long!
This is a real necessity, especially considering that tags are the only option we have to create hierarchies that are deeper than one level.
I'm having the same issue, also a premium user. Reboot and reinstall do not fix the problem.
I'm on macOS Sierra 10.12.3 and Evernote 6.10 (direct download).