A set of userChrome.css styles for Firefox UI:
phd-userChrome-active-tab-accent-background.cssphd-userChrome-active-tab-double-min-width.cssphd-userChrome-auto-hide-navigation-and-bookmarks.css(experimental)phd-userChrome-bookmarks-styling.cssphd-userChrome-disable-proton-ui.cssphd-userChrome-findbar-styling.cssphd-userChrome-floating-menubar.cssphd-userChrome-floating-notifications.cssphd-userChrome-fullscreen-toolbars.cssphd-userChrome-kde-breeze-icons.cssphd-userChrome-menu-items-styling.cssphd-userChrome-multiline-bookmarks.cssphd-userChrome-places-window-horizontal-layout.cssphd-userChrome-remove-megabar.cssphd-userChrome-smaller-items-in-extensions-panel.cssphd-userChrome-tabs-styling.cssphd-userChrome-toolbars-order-and-styling.css
ALL.css includes all non-experimental styles.
cd ~/.mozilla/firefox/*.default-release/
mkdir -p chrome
cd chrome
git clone https://github.com/phd/phd-userChrome
echo '@import "phd-userChrome/ALL.css";' >> userChrome.css
Navigate to about:config and set toolkit.legacyUserProfileCustomizations.stylesheets to true.
You may also want to set:
browser.compactmode.showtotrueandbrowser.uidensityto1browser.tabs.inTitlebarto0browser.toolbars.bookmarks.visibilitytoalways
Restart Firefox browser.
cd ~/.mozilla/firefox/*.default-release/chrome/phd-userChrome/
git pull
Restart Firefox browser.