Firefox's userChrome.css for some tweaks, viz., show bookmarks bar and no address bar enlargement

userChrome.css

/* 
Show bookmarks on address bar focus (and thus show automatically when a new tab opens)
From https://superuser.com/a/1520406
Original source https://www.reddit.com/r/FirefoxCSS/comments/emzoi0/show_bookmarks_bar_only_in_new_tab_page/feme6yv/
*/

#nav-bar:not(:focus-within) + #PersonalToolbar:not(:hover):not(:focus-within):not([customizing]) { visibility: collapse; }


/* 
Remove address bar enlargement 
From https://superuser.com/a/1540382
Based on https://old.reddit.com/comments/fwhlva//fmolndz
*/

#urlbar[breakout][breakout-extend]:not([open]) {
    top: calc((var(--urlbar-toolbar-height) - var(--urlbar-height)) / 2) !important;
    left: 0 !important;
    width: 100% !important;
}

#urlbar[breakout][breakout-extend]:not([open]) > #urlbar-input-container {
    height: var(--urlbar-height) !important;
    padding-block: 0px !important;
    padding-inline: 0px !important;
}

#urlbar[breakout][breakout-extend][breakout-extend-animate] > #urlbar-background {
    animation-name: none !important;
}

#urlbar[breakout][breakout-extend]) > #urlbar-background {
    box-shadow: none !important;
}

Works for 78.3.0esr-2.