The "clean" button is confusing. There's no indication of what it does since it doesn't seem to affect the current domain. I always use the dropdown to do the cleaning I want.

It was confusing that this isn't like Self-Destructing Cookies in that cleaning cookies and localstorage when you leave a domain isn't enabled by default. But worse, even when that's enabled, it doesn't work properly. I keep having to use the option to manually clean cookies for domains I last visited days before (mainly news sites that give a limited number of articles per month and warn me that I have only one article left). I have an older system with the Self-Destructing Cookies extension and it has no such problems with the exact same sites.