In Showbie, you can sort or reorder your folders however you'd like similar to how you can reorder posts in the Shared Items list.
While in a class, tap on the wrench icon
Tap Manage List
In this mode, you can reorder folders however you'd like; look for the reorder handle (the 3 lines) on the right side of the folder name
You can tap and hold to reorder the folders
Need to change the name or colour of the folder? Learn more here.