We've just rolled out our new folder management screen to all our production servers. You can access it either via the Options screen then the Folders link, or from the (Edit/Refresh) link at the top of the folder tree on the Mailbox screen immediately after logging in.
The new screen makes it much easier to create sub-folders of other folders, to move and rename multiple folders, and includes many new features that can be controlled for each folder.
Additionally it's much easier to edit multiple folders at once, including the ability to set many or only a few specific features/properties on a large set of folders at a time.
If you have any comments or encounter any problems with the new screen, please post to our forum thread here.