How do you find out what Firefox Profile is running when Firefox is running?

Question

Is there a variable, or an about:config setting, or an add-on that will tell you what Firefox profile you are running when Firefox is running?

So I can come back to Firefox like 3 days later and know that these Windows are for this and those windows are for that...and these plugins are installed in this profile and those plugins are installed in that profile....

Answer 1

Enter "about:support" as URL and select the "Open containing folder" button. You can reach it using Menu "Help" -> "Troubleshooting Information", too:

(Screenshot by lifehacker.com)