Due to the way Firefox works, you can not have mixed private browsing and normal browsing modes open with the same instance of Firefox. It is possible to use the 2 modes simultaneously but it involves a bit of work.

You can get something similar by creating a new profile folder. Firefox stores user data such as bookmarks and passwords in a profile folder. It is possible to run 2 different profiles at the same time, one in normal browsing mode and the other in private browsing mode.

For details of how to create a new profile see http://kb.mozillazine.org/Creating_a_new_Firefox_profile_on_Windows

Once you have created the new profile, you can set up a shortcut to launch the different profiles, for details on how to do that see http://kb.mozillazine.org/Shortcut_to_a_specific_profile

Next to let you use the 2 profiles at the same time you need to use the -no-remote command line argument as shown here - http://kb.mozillazine.org/Opening_a_new_instance_of_your_Mozilla_application_with_another_profile

You can set up one profile to always open in private browsing mode. For details of how to do that see https://support.mozilla.com/en-US/kb/Private%20Browsing#w_how-do-i-always-start-firefox-in-private-browsing

I told you there was a bit of work involved :)

A possibility is to enter Private Browsing mode via:

• Tools > Options > Privacy [X] "Permanent Private Browsing mode"

To see all History and Cookie settings, choose: Tools > Options > Privacy, choose the setting Firefox will: Use custom settings for history

This will enter PB mode (gives you a new set of cookies) without closing tabs, but still adds entries to recently closed tabs and windows. Removing the check mark and closing the options window will restore the previous cookies from regular mode.

(also looking a solution) There was an addon that did exactly this but it's discontinued now. It probably worked the same way as you laid out here. Now is there another add-on that does the same thing?

Hey TonyE, that was really helpful. Thank you. :)