In the Exec lines of desktop files exported by Flatpak, the field code for the file/URL to be passed to the application is surrounded by @@:
Exec=/usr/bin/flatpak run --branch=stable --arch=x86_64 --command=blender --file-forwarding org.blender.Blender @@ %f @@ What does this mean? The spec doesn't mention it and the desktop files in /usr/share/applications don't contain it either.
--file-forwarding
If this option is specified, the remaining arguments are scanned, and all arguments that are enclosed between a pair of '@@' arguments are interpreted as file paths, exported in the document store, and passed to the command in the form of the resulting document path. Arguments between '@@u' and '@@' are considered uris, and any file: uris are exported. The exports are non-persistent and with read and write permissions for the application.
