We are frequently receiving requests to be able to manage subfolders. We plan to implement this shortly.
For all Dropbox users there is an easy trick on how to do this now already:
Using a "/" in the folder-name Dropbox will automatically create a main and a subfolder for you. So for example creating a Drobpx Wok with the name "main/sub"
Will cause a "main" folder with a "sub" subfolder to be created in your Dropbox
This is just a DropBox workarround. So in future we will work on other services to support subfolders as well. The enhancement will also include propper interface elements to manage subfolders.