#toolbar-menubar {height:30px !important}

How does the menu bar currently show for you? Can you attach a screenshot? *https://support.mozilla.org/en-US/kb/how-do-i-create-screenshot-my-problem *use a compressed image type like PNG or JPG to save the screenshot You can add CSS code to <b>userChrome.css</b> in the chrome folder in the Firefox profile folder to adjust the height of a toolbar. You can familiarize with the Browser Toolbox to inspect and modify elements in the user interface. *https://firefox-source-docs.mozilla.org/devtools-user/browser_toolbox/ <hr> <pre><nowiki> #toolbar-menubar {height:30px !important} </nowiki></pre> <hr> It is not that difficult to create <b>userChrome.css</b> if you have never used it. The first step is to open the "Help -> Troubleshooting Information" page and find the button to access the profile folder with the random name (xxxxxxxx.default-release). *https://support.mozilla.org/en-US/kb/use-troubleshooting-information-page-fix-firefox You can find the button to go to the profile folder under the "Application Basics" section as "Profile Folder -> Open Folder". If you click this button then you open the profile folder in the Windows File Explorer. You need to create a folder with the name <u>chrome</u> in the profile folder with the random name (name is all lowercase). In the <b>chrome</b> folder you need to create a plain text file with the name <b>userChrome.css</b> (name is case sensitive). In this userChrome.css text file you paste the text posted. On Mac you can use the TextEdit utility to create the userChrome.css file as a plain text file. In Windows saving the file is usually the only time things get more complicated because Windows can silently add a .txt or .css file extension and you end up with a file like <i>userChrome.css.txt or userChrome.css.css</i>. To avoid this, you need to make sure to select "All files" in the "Save File" dialog in the text editor. You need to close (Quit/Exit) and restart Firefox when you create or modify the userChrome.css file. More info about userChrome.css/userContent.css in case you are not familiar: *https://www.userchrome.org/what-is-userchrome-css.html *https://www.userchrome.org/how-create-userchrome-css.html *https://www.userchrome.org/firefox-changes-userchrome-css.html You need to set this pref to true in about:config to enable userChrome.css and userContent.css in Firefox 69+. *about:config => toolkit.legacyUserProfileCustomizations.stylesheets => true *https://support.mozilla.org/en-US/kb/about-config-editor-firefox