bookmarks toolbar reduce horizontal icon spacing
For anyone who wishes to reduce horizontal spacing between bookmark icons in the horizontal Bookmarks Toolbar across the top of Firefox window (under the address bar), here is the code to add to userChrome.css:
/* Bookmarks Toolbar icon horizontal spacing */
toolbarbutton.bookmark-item:not(.subviewbutton) {
padding: var(--bookmark-block-padding) 3px !important;
}
The default value is 4px. I changed it to 3px. You can change this number as you like.
Remember to save the css file, close and then re-open the browser to view the update.
There is also a way to play with this live if you access the Browser Toolbox: https://developer.mozilla.org/en-US/docs/Tools/Browser_Toolbox and access userChrome.css: https://developer.mozilla.org/en-US/docs/Tools/Style_Editor
Hope this saves someone the hours I spent finding this solution. Cheers!