1. Click the folder you want to rename in the Workspace pane.
2. Go to File --> Rename... from the top menu to open the Rename item form.
3. Enter the new name into the Rename item to field.
4. Click Rename to accept.
You can rename folders and sub-folders containing opened but unsaved files. You can save them after renaming the folder, no data will be lost.
If the new folder name already exists in the target folder, you will receive an error message as below.

You cannot rename the workspace root folder.
Remember to undeploy all earlier deployed REST Services within the moved folder or sub-folder before renaming the folder.