All the incognito browser windows share the same "session" in Firefox. So say you open an Incognito window to browse Facebook or something, then you open another Incognito window, this new incognito window is linked to the previous incognito window, meaning you are logged into Facebook at that new Incognito window as well. This is because, as I explained before, all the incognito windows share the same "session"
The only way to clear incognito window is to close ALL of them and then create a new incognito window. You dont have to close the main non incognito Firefox window though, just close all the incognito windows. Then open a new one, now your previous session is destroyed and you are new again.
You may know it but its not that common knowledge as it should have been
Btw, a good addon for doing that all the time is Cookie AutoDelete. Building up the whitelist will take a while, but it's worth it in the end.
Thanks for the recommendation.
I believe it adds some features above Firefox's defaults, but for anyone reading that doesn't know, Firefox does have a feature
"Delete cookies and site data when Firefox is closed." under "Privacy and Security" in settings -> under the "Cookies and Site Data" sub-section.
They also have a "Manage Exceptions" button to build a whitelist and blocklist of websites to always allow cookies and site data, or always block cookies and site data.
For those looking for more extreme add-ons are a great idea, but always prefer built-ins when available/sufficient.
I'm fine with just using Private browsing in my case. My wife knows I look at porn, but I don't want it to be in her face if she ever uses my computer.