This is an issue that has been brought up before back in 2012 and continues to exist. I use Outlook for Mac 2011,  version 14.6.

 Like other users, I rely heavily on managing my emails using the subject category folders. From time to time I edit obsolete folders with new topic headers or attempt to create new ones. This normally works but recently when I tried to edit some email folders, and type in the new folder name, the folder does not update and I cannot hit a return to execute the command. Similarly, when I go to enter a new folder as a sub category, the same thing happens.

-Mike  (*** Email address is removed for privacy ***)