It is currently not possible to create a Subfolder via the client!!! Please do not try to create a Subfolder via client since this could lead to major damage!!!
To create a Toplevel Folder via Client
1. Click on Create Folder.
2. A window will open up now. Enter the name of the new folder by adding: \foldername in the directory bar and clicking on OK.
The Toplevel Folder created in the above shown picture would be called ExampleFolder.
3. Done. The folder is now ready to be shared with other people.
Click on Explore to open the Top Level Folder.
Click on Invite to share the Top Level Folder with other users.
Click on Finish to close the wizard.