I would like the Firefox profile manager to open when I run Firefox from the GNOME 3 menu, be it the DashBar or the native menu. I installed Firefox using Flatpak.

I know that I can run it from the terminal with flatpak run org.mozilla.firefox -p. But how do I modify the .desktop file? I guess it is the one in /var/lib/flatpak/exports/share/applications/org.mozilla.firefox.desktop? I tried replacing the line

[Desktop Entry]
Exec=/usr/bin/flatpak run --branch=stable --arch=x86_64 --command=firefox --file-forwarding org.mozilla.firefox @@u %u @@

with

[Desktop Entry]
Exec=/usr/bin/flatpak run --branch=stable --arch=x86_64 --command=firefox org.mozilla.firefox --ProfileManager

but I cannot save the document because of “too many symbolic links”.

What is the secret?

I really wish Firefox would simply offer this as an option in its settings.