I think this depends a bit on from where you are starting your script now.
The external folder is not equal to the site-packages folders that are automatically in your system path. And I figured out that e.g. running a file for doctest purposes and compared to the standard results is totally different path structures. External folders might be outside the Pythonista app folder structure.
import sys sys.path
To see if the files you are looking for are actually on this path. Best add a simple test python in the same folder.
I was reading many posts however not able to grasp it logically.
Basics: iOS 13.4.1, Pythonista 3.3
In the scene examples you’re using build in images with a shortcut or constant to the path defined, like 'plc:Character_Boy' - I understood that the plc: is like the folder and reference.
Now above there is a “Files” folder in this (+) dialog and based on the posts and documentation I assumed after importing + in the file browser I can finde the images there. But no, I see them in the file browser but not in the (+) files list.
Some hint regarding how it is supposed to be would be great.