OctoPrint v1.3.0 is now out with very great new features.
One of these features is the new file manager, which now supports the creation of folders.
I’m doing all my best to support this feature in Printoid. But for the moment, if you have installed Printoid v5.11 on your device, you will only see the folders in the file list, without the possibility to see the files inside of theim.
For the moment, if you wanna continue to use Printoid, I want to advise you to keep your files outside of any folder until I release the v5.12.
[EDIT] The v5.12 is now out ! https://printoid.net/2016/12/09/401/
Thanks a lot for your comprehension, your patience and your support!