Firefox script to move tabs, address bar, etc to the bottom.

userChrome.css

@-moz-document url(chrome://browser/content/browser.xhtml) {
	/* tabs on bottom of window */
	/* requires that you set
	 * toolkit.legacyUserProfileCustomizations.stylesheets = true
	 * in about:config
	 */
	#mainPopupSet ~ box { -moz-box-ordinal-group: 10; }
	#titlebar { -moz-box-ordinal-group: 10; }
	#urlbar {
		top: unset !important;
		bottom: calc((var(--urlbar-toolbar-height) - var(--urlbar-height)) / 2) !important;
		box-shadow: none !important;
		display: flex !important;
		flex-direction: column !important;
	}
	#urlbar-input-container {
		order: 2;
	}
	#urlbar > .urlbarView {
		order: 1;
		border-bottom: 1px solid #666;
	}
	#urlbar-results {
		display: flex;
		flex-direction: column-reverse;
	}
	.search-one-offs { display: none !important; }
	.tab-background { border-top: none !important; }
	#navigator-toolbox::after { border: none; }
	#TabsToolbar .tabbrowser-arrowscrollbox,
	#tabbrowser-tabs, .tab-stack { min-height: 28px !important; }
	.tabbrowser-tab { font-size: 80%; }
	.tab-content { padding: 0 5px; }
	.tab-close-button .toolbarbutton-icon { width: 12px !important; height: 12px !important; }
	toolbox[inFullscreen=true] { display: none; }
}