4wd: "Wouldn't it be a lot less complicated, (and cheaper), to have the browser delete cookies when it's closed, (ie. they all become session cookies) ?"Firefox provides an option to delete all cookies when the browser is closed (Options/Privacy & Security/Cookies and Site Data/Keep Until...Firefox is closed).
Hence my question above; unfortunately, the traditional FF add-in having brilliantly done exactly that not working anymore beyond FF 56 (or whatever the exact version number was).
A more flexible solution is to leave the setting at the default "...Until they expire" and use a cookie whitelist extension to determine which ones to keep or delete. Two such extensions that work well for me are "Cookie AutoDelete" and "Forget Me Not," both of which are compatible with current Firefox versions.
