I've renamed my folders successfully on a few occassions in Airwave 8.X (not sure if this feature has always been present). You have to go to the "Parent Folder" of the folder you want to rename.
- Navigates to APs/Devices
- Go to folder: (Select Parent Folder)
- Scroll down the page past client/usage/devices list statistics, and you should see a list of the Child Folders, one of them being the one you want to rename.
- Click the Edit (Pencil Icon) beside the folder you want to rename.
- Modify the Folder Name and Click Save.
I've done this several times over the past few months, and haven't had any issues. *Note though we only use Airwave currently for monitoring/data retention - (No configuration management). Not sure if there's any negatives/potential issues this might cause.