Actual behavior:
Using the XNAT Tree Browser, it is currently not possible to directly add a custom folder under the "Resources" folder, while the "Resources" folder is selected in the tree view.
The right click context and the item for folder creation are disabled on the "Resource" folder level. You have to create the folder on the "Experiment" level.

Expected behavior:
Intuitively the user selects the "Resources" folder and wants to add a subfolder, specifying a custom folder name. The new folder is then created under the "Resources" folder.