Firefox (till at least v147.0. - January 16th 2026) - Tabs Below Address -and Bookmark Toolbar
*Last update: Still works 16 January 2026, Firefox version 147.0*
Every now and then Mozilla makes updates for Firefox that makes the userChrome file not working anymore. In this file you can make changes regarding the layout. In the link mentioned below you will find the exact code you need to copy into the userChrome.css file. This code will not only put your tabs below the address bar, but also below the bookmarks toolbar AND it will make your bookmarks more compact, so more txt is visible.
The link leads to a large Tech related Dutch board, known as Tweakers and I posted there the code that is needed for your userChrome.css file. Just click on the link and you can copy the code straight from there. You also need to do another thing, which is the following (otherwise the 2nd part of the code won't work), which is stated below: don't forget this little setting.
Go in your browser and type: About:config
Type in the bar: toolkit.legacyUserProfileCustomizations.stylesheets
Turn this option to : TRUE
Direct link:
https://gathering.tweakers.net/forum/...