Cannot develop extensions using external files

[felciano]

I'm trying to get Working Copy integration with Pythonista via the "External Files" functionality, so that code can be stored in Github. I am able to access Github repositories to edit and run code from the main Pythonista window, but I can't figure out how to expose one of these scripts as a Share Sheet script in Pythonista.

In particular, when I'm looking at one of these scripts and choose the little gear icon and tap "Shortcuts... > Share Extension > + [new share extension]", it prompts me to pick the script for the new share extension and my only options are "This iPad" or "iCloud". Is there a way for the scripts under "External files" to be selected?