Did you try code in userChrome.css?

• https://www.userchrome.org/how-create-userchrome-css.html
• https://www.userchrome.org/what-is-userchrome-css.html

Yes, several scripts listed here and elsewhere. Nothing worked.

Did you try other code in userChrome.css in case there is a problem with the file?

I personally use this code: Add code to the userChrome.css file below the default @namespace line.

@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"); /* only needed once */

/* tabs on bottom */
#navigator-toolbox toolbar:not(#nav-bar):not(#toolbar-menubar) {-moz-box-ordinal-group:10}
#TabsToolbar {-moz-box-ordinal-group:1000!important}

It is not that difficult to create userChrome.css 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.

• https://support.mozilla.org/en-US/kb/use-troubleshooting-information-page-fix-firefox

You can find this button 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 chrome in this folder (name is all lowercase). In the chrome folder you need to create a text file with the name userChrome.css (name is case sensitive). In this userChrome.css text file you paste the text posted.

In Windows saving the file is usually the only time things get more complicated because Windows can silently add a .txt file extension and you end up with a file named userChrome.css.txt. To avoid this you need to make sure to select "All files" in the dialog to save the file in the text editor using "Save File as".

You need to close and restart Firefox when you create or modify the userChrome.css file.

Used the script above in userChrome.css within folder "chrome" within profile folder and was careful to save as 'all files'. Still tabs on top.

Does code like this in the file to set the font-size in the location bar work?

#urlbar .textbox-input-box {font-size: 14pt !important; font-family: monospace !important}