I don't know much about cookies but this extension seems to be fine …

Complimentary to Cookie AutoDelete.

@tulirebane
I believe your problem comes from websites which make use of a third-party to manage the logging-in.

From what I understood from this extension's description, the point is to keep only the most important cookies after an user action, like a login session.

However, after testing this on a cookie-fresh profile, I found out that it doesn't work as should - I got signed out from at least three sites (Reddit, Google and Slack).

Besides, it seems to be useless on a cookie-filled profile, do consider adding a button to apply the extension rules on existing cookies.