This should be possible with userChrome.css
. I found this Github where there are a lot of customizations for Firefox available: https://github.com/Aris-t2/CustomCSSforFx
One that stood out was addonbar_extra_bookmarks_toolbar_below_navbar_fx65.css
. If you add its code to your userChrome.css
file, it will add another bar below the navigation bar.
/* create an empty space below navigation toolbar */
/* Firefox Quantum userChrome.css tweaks ************************************************/
/* Github: https://github.com/aris-t2/customcssforfx ************************************/
/****************************************************************************************/
#main-window:not([customizing="true"]) #nav-bar {
padding-bottom: 26px !important;
}
/* reduce maximum width of location bar and search bar on navigation toolbar */
#main-window:not([customizing="true"]) #nav-bar :-moz-any(#urlbar-container, #urlbar, #search-container, #searchbar) {
min-width: 50px !important;
}
/* move bookmarks to empty space below navigation toolbar, if on navigation toolbar */
#main-window:not([customizing="true"]) #nav-bar #personal-bookmarks {
position: absolute !important;
bottom: 1px !important;
min-width: 0 !important;
width: auto !important;
max-width: 100vw !important;
}
/* reduce size of bookmarks 'more bookmarks' menu chevron and remove its background color on navigation toolbar */
#nav-bar #personal-bookmarks #PlacesChevron .toolbarbutton-icon {
min-width: 0px !important;
min-height: 0px !important;
width: 16px !important;
height: 16px !important;
padding: 0 !important;
margin: 0 !important;
background: unset !important;
box-shadow: unset !important;
}
/* set minimum height for bookmarks, when on navigation toolbar */
#nav-bar #personal-bookmarks toolbarbutton.bookmark-item:not(.subviewbutton) {
min-height: 24px !important;
}
/* adjustments */
#nav-bar #personal-bookmarks {
min-width: 40px !important;
width: auto !important;
max-width: 50vw !important;
}
Now you will have to move the Bookmarks Toolbar Items into the navigation bar using Firefox's customize option. Then you can use the bar just for add-ons, just drag them down.
I only have one add-on on this browser so it's not a great test but I can test more once I get home.
about:config > toolkit.legacyUserProfileCustomizations.stylesheets > true
(from the GitHub link)Also nice is https://www.jeffersonscher.com/gm/url-bar-tweaks.html