A WebExtension version (in essence) of the ever-popular Self Destructing Cookies and the better-but-not-as-popular Cookies Exterminator. My only suggestion -- which is found in CE -- is a "greylist" feature, for cookies that best remain until the browser is closed. I don't like having the cookies cleared, say, every three hours (every five minutes tops), but I don't like being perma-logged in for certain things (such as email, or banks, or government pages with logins and odd redirects that are so slow that the cookies get cleaned right there and then and I get basically kicked out midway through checking and paying for my water bills THANK YOU GOVERNMENT).

Can't wait for a Fennec version once the appropriate things are ready over there (APIs, no?).