Awesome design decisions
I do not have much time to write these days, but this situation made enough annoyance for me to warrant this content.
First, kudos to Firefox team for well maintained browser.
In general, I am one of the stubborn one, who do not like fluidity of Chrome and its ever changing behaviour. In the past, IE and Microsoft was the one breaking standards. Now it appears that these great minds moved to Google and every new version of Chrome will give you something new and unexpected from great wisdom of all-knowing and all-seeing company. 🙂
Firefox team seems to feel the pressure and joined the party of making users happier by delivering surprising features.
In last few months one of the great things to appear was expanding/enlarging address bar.
There is probably some great reason for it to behave this way, and I respect the decision Firefox UX team made, but it is really distracting.
In Firefox 75 and 76 advanced users could use about:config settings to suppress this behaviour, but it was taken away in Firefox 77, so I will skip referencing solution there and instead focus on awesome 77+ build and we would need to do some coding.
Taking control back
Chrome is creeping in. No way to avoid its influence these days.
As with Chrome, you can define your own CSS styles for Firefox as well, if you know the tags.
First, you need to enable CSS styles overrides for Firefox.
Visiting userChrome.org will help you with step by step instruction on how to do that here.
Once you give yourself tools, next step is to start using them – override how address bar is styled.
From the same site, you can grab ready to go userChrome.css file which will return your bar under control here then drop it into chrome folder under your Firefox user profile folder. It is important that you create chrome folder if it does not exist before placing CSS there.
After making sure toolkit.legacyUserProfileCustomizations.stylesheets is set to true in your about:config and restarting the Firefox, you will get your address bar back.
PS: Additional candy is that reviewing the CSS will tell you exactly how to modify the bar in any other way you like. Fave fun, give it color, make it big to take half the screen, go crazy. Just kidding.