File system sync on removable-media

This flatpak only have permission to access user's home directory.
Need to 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.

Fractional scaling under Wayland

Wayland support is already implemented but disabled by default.

You can enable it with Flatseal by checking the "Wayland windowing system" toggle or by running the command below:

flatpak override -u net.cozic.joplin_desktop --socket=wayland

Use external editor with flatpak

There are two ways.

xdg-open

Nothing need to be done, it's done by electron.
Joplin will open a dialogue to select editor.

• How to reset the xdg-open choice
  flatpak permission-remove desktop-used-apps text/markdown net.cozic.joplin_desktop

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 command>

example

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

# run native app
--host /bin/gedit