browdyconsulting said

Found a few suggestions to go to View, Toolbar, Customize and uncheck the "use small icons" box in the overflow menu. Sadly, there is no "use small icons" box there.

Those suggestions about "use small icons" is rather dated. That preference feature was removed ages ago.

Currently the use of an optional userChrome.css file with the proper code is needed to effect that type of modification to the UI.

https://www.userchrome.org/ Discussions about the .css modification code are here: https://www.reddit.com/r/FirefoxCSS/

You can set layout.css.devPixelsPerPx to 1.0 (default is -1) on the about:config page. Adjust its value in 0.1 or 0.05 steps (1.1 or 0.9) until icons or text looks right. Modifying layout.css.devPixelsPerPx affects user interface and web pages (global zoom). You can use an extension to correct the appearance of web pages.

You can look at Zoom Page WE and NoSquint Plus extension to set a default font size and page zoom on web pages.

• [51]https://addons.mozilla.org/firefox/addon/zoom-page-we/
• [42]https://addons.mozilla.org/firefox/addon/nosquint-plus/