This is an old revision of the document!
Prevent Firefox from starting automatically - https://support.mozilla.org/en-US/kb/firefox-starts-automatically-when-i-restart-window
about:profiles
better formats
https://support.mozilla.org/en-US/products/firefox/sync-and-save
https://support.mozilla.org/en-US/kb/send-tab-firefox-desktop-other-devices