Go to the Mozilla Add-ons Web Page {web Link} (There’s a lot of good stuff here) and search for what you want.

Exactly what functionality do you want from the "Status Bar" at the bottom of the browser window?

While there are a number of Add-ons available, none actually "restore" the old Status Bar that was available prior to Quantum which was released in Nov 2017.

Hello doodlemuffin,

You could add code to a userChrome.css file :

http://www.optimiced.com/en/2018/02/11/restore-status-bar-in-firefox-quantum/

Note : Scroll all the way down for the code that will work with the latest Firefox version.