As a user, you create them - simply right click on the folder named "User managed user folders" and click on the option "Create Sub Folder..."
You can manage them (Edit, Rename, Delete) - simply right click on the folder to manage and click on the corresponding option "Edit..." or "Rename..." or "Delete..."
You can create sub folders under a folder to any level of nesting - simply right click on the folder under which to create sub folder and click on the option "Create Sub Folder..."
Only the lowest level folder can contain any sales in it
You can drag/drop sales into the lowest level folder
You can also use menu option to add selected sales to a folder (instead of drag/drop)
To display the sales in a folder, simply click on it
By default, when you create this type of Folder, same folder is ALSO automatically created for Listing Templates and Listings. To change this behavior, change your preferences.