I use Firefox Beta on Android. Recently there was a change so that a second bar appeared on the screen. I have the URL bar at the top of the screen, and suddenly a second bar appeared at the bottom of the screen with back, forward, tab and new tab buttons. I got used to this and really liked it. However it has now disappeared. I am wondering if there is a setting which I can use to get the second bar back, but I don't know where to start looking. Is there changelog for beta releases which I could look at to work out what this bar even was?

Thanks.