Dont know if you mean the same as I expected at first:
I thought Joplin synced directories where it stored markdown files. So if I added a Markdown file via Explorer (Win) it would show up in all clients.
Or in Joplin it would show the folders with *.md as a tree structure of notebooks and subnotebooks.
Instead it uses sync the distribute everything in a sort of “app-data” storage. (Afaik)
When I started with Joplin I used bulk import of MD.
I use the bulk export feature once a month or so to create all md files as an extra backup.
But I dont interact with md files directly anymore.
let me try that export feature into Android. I did almost similar as you described.