da2x / net.cozic.joplin_desktop

File system sync on removable-media

This flatpak only have permission to access user's home directory.
Need manually add permission to allow access other location.

You can do it with Flatseal, and configure permissions with nice gui.
Or use terminal command:

flatpak override --filesystem=host net.cozic.joplin_desktop

Note: You can also use multiple filesystem options to set /media,/run/media,/mnt as you need.

Use external editor with flatpak

There are two ways.

xdg-open

This will open a dialogue to select editor.

Path:
/bin/xdg-open

flatpak-spawn

This can run command outside flatpak, which means this flatpak most likely to be unsandboxed.
This feature is enabled for full external editor support.

Path:
/bin/flatpak-spawn
Arguments:
--host <outside flatpak command>

example

Path: 
/bin/flatpak-spawn
Arguments: 
--host /bin/flatpak run --filesystem=xdg-config/joplin-desktop org.gnome.gedit