> Joplin isn’t designed for your notes to be modified outside of the ecosystem, the notes themselves are markdown so you can export or transfer them, but you can’t simultaneously edit them outside of Joplin.
With that feature the external editor is launched via Joplin, so the editing is still happening in the ecosystem. You can’t just open the notes from outside Joplin.
Well, except for https://joplinapp.org/help/apps/external_text_editor/