Is there a way to add a second account to firefox (like in google chrome) to have 2 separate windows, each with its own history, cookies, etc. )

Hello lome, You can do so by creating different profiles for each user, see : https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles And also : https://www.howtogeek.com/209320/how-to-set-up-and-use-multiple-profiles-user-accounts-in-firefox/