As you know, mu plugin's main file must be presented directly in mu-plugins folder without sub folder. Then such plugin can just include it's another files in sub folders using
As I understand your plugin can scan for translations only main file. I clicked 'Scan' button and got strings for translation only from main file.
Can you add possibility to scan sub folders too? Maybe it will be some question to user, and he will choose folder or enter folder directory by himself.