A Microsoft application for managing email, calendars, contacts, and tasks across devices and platforms.
Today when I tried to repeat the steps so I could write a reply, everything worked as expected. There haven't been any updates in the last two days, no change in build numbers or anything else. Maybe having shut down Windows and the VM to do a backup the host? I don't know... (Have you ever taken a car to a mechanic and not been able to get to make that noise again? Taken a sick kid to a doctor and suddenly they're in perfect health?)
Anyway, the steps are exactly like adding any group or button to the ribbon, except that I chose the "Macros" item in the dropdown on the left side and selected my macro in the list. Both the custom group and the macro command should enable the Rename button -- and now they do.
Sorry for the false alarm!