There is no built-in way to add or expand bars, but I'm curious which one you mean: the bar with the tabs for open pages, the main toolbar (address bar, buttons), or the Bookmarks Toolbar (favorites)?

I was referring to the Bookmarks toolbar. Mine is full, and I need to add 4 or 5 more bookmarks. that's why I hope that one could add one more row without having to use >> to bring up the missing (hidden) bookmarks. Thanks for your help!

See:

• https://github.com/MrOtherGuy/firefox-csshacks/blob/master/chrome/multi-row_bookmarks.css
• https://www.userchrome.org/what-is-userchrome-css.html
• https://www.userchrome.org/how-create-userchrome-css.html

In Firefox 69 and later you need to set this pref to true on the about:config page to enable userChrome.css and userContent.css in the chrome folder.

• toolkit.legacyUserProfileCustomizations.stylesheets = true
• https://www.userchrome.org/firefox-changes-userchrome-css.html

See:

• https://github.com/MrOtherGuy/firefox-csshacks/blob/master/chrome/multi-row_bookmarks.css
• https://www.userchrome.org/what-is-userchrome-css.html
• https://www.userchrome.org/how-create-userchrome-css.html

In Firefox 69 and later you need to set this pref to true on the about:config page to enable userChrome.css and userContent.css in the chrome folder.

• toolkit.legacyUserProfileCustomizations.stylesheets = true
• https://www.userchrome.org/firefox-changes-userchrome-css.html

Oh, I had never touched that console-type code but the resources you posted are very explanatory and easy to follow. So i did the whole thing and it worked splendidly. I'm so happy with the result. Thank you for your time!