Thanks for the explanation
So basically it concerns file:/// cookies which are mostly not to worry about since there is no privacy concern to be had with HTML pages that are stored on our own HDD, unless they do XmlHttpRequests from file:/// to an external domain, assuming Firefox allows this in the first place which I don't know.
Still, individual file permissions versus allowing any file:/// document to store cookies is an improvement, so I'm glad you enabled it by default and are keeping an eye on Firefox's new implementation (which will deprecate the current one, making Cookie Controller obsolete in this area if you weren't there to update it)
About Synaptics TouchPad, I was not sure it was considered a Trackpad (I don't know exactly what a Trackpad is), that's why I mentioned the name of my equipment. It's not even Apple related.
Ctrl-left-clicking on the Perm button *should* do something special. If you don't currently have an exception set for that web site, it should set the default exception *temporarily*. Temporarily usually means until you close or restart Firefox, although there are hidden preferences to set timed exceptions. It also works on the permissions on the menu. If you have an exception set already, ctrl-clicking does nothing because you can't temporarily remove an exception. Maybe it should do something, be a normal left-click like on the Tidy button?
Good to know about the temporary exception! As for your final question, CTRL+LeftClick is not really part of my habits so I'm not fit to reply. Maybe it would be useful for someone with a Trackpad but I don't know what kind of user experience they have.
An import/export option would be nice indeed! I hope Firefox will soon be ready with IndexedDB permissions as well, so Cookie Controller can cover it.
Those are the only two features I can think of that are really missing.