Tkinter File Selector is Buggy #215
Description
The Tkinter file selector, when you launch GuPPy, remains open even when the main web app has been launched, which can cause the area around the pop-up to become unresponsive. To avoid this problem, GuPPy should move the file selector logic inside the panel widget instead of using Tkinter.
A key constraint of this selector is that it needs to be able to select folders both on the local drive and on external hard drives.