The new folder is created, and you can create new folders according to the same principle.
The new folder is always saved in the selected folder.
To the right of the folder name you now have two menu buttons to choose from.
With

you can delete the folder. (Attention: The card sets contained in this folder will also be deleted. Before you delete a folder that still contains flashcards, you should move the flashcards first.)
With

you can rename the folder.