Cookiebro is probably the best cookie manager for Firefox and Chrome, built on the bones of the now-abandoned Vanilla cookie manager extension (which I missed). I highly recommend it.

Cookiebro is easy to use, and relatively intuitive. Keep cookies in whitelists and block cookies in blacklists, and easily purge the rest cookies on-demand or automatically. Import or export lists as a simple text file that is simple to edit. The cookie log view and cookie editor are powerful tools whether managing privacy or just debugging.

Minor issues: While adding and removing list items is easy, one can't edit them in place. For example, if I have "getpocket.com" in my whitelist, and want to change it to "*.getpocket.com", I have to add the latter as a new element, and then remove the former. I also wish the extension would sync settings across browsers, so I didn't have to spend as much time importing and exporting.

For managing and auto-deleting cookies, also try the Cookie AutoDelete (CAD) extension. Choosing between that and Cookiebro is a matter of personal preference. I have found CAD to be a bit buggier, but it has some advantages of its own. While it lacks the Cookie Log and Cookie Editor, these aren't essential for the majority of users.

For those who are cautious about their extension use, the developer (Nodetics) has at least one other extension that is Mozilla Recommended, and I suspect Cookiebro has not yet been recommended largely because the UI is perhaps too minimalist and functional, with less frequent updates.