Sub Folder Creation

I see it has featured here before but is it yet possible to create sub-folders? Without this facility my client cannot use PP. They are planning to post Lesson Plans for a year long course so it just won't work with all files in one directory.

PP comes with default folders named "documents", "images", and "other". These three can be renamed or deleted and new folders can be created. All folders are however at the "root" level, there are no sub-folders. Collabtive is very similar to ProjectPier and it allows sub-folders, although I think the way they have implemented file handling in Collabtive is little clunky to use.