userChrome.css (minimal)

#TabsToolbar      { background: #1c1b22 !important; color: #ccc !important }
.tabbrowser-tab   { max-width: 200px !important; padding: 0 !important }
.tab-background   { border-radius: 0px !important }
.tab-label        { opacity: .8 }
.urlbar-input-box { font: bold 13px Lato; opacity: .7 }

#urlbar-input-container,
#nav-bar-customization-target
{ border: none !important; background: #1c1b22 }

#TabsToolbar   { margin-left: 29vw }
#nav-bar       { margin-right: 71vw; margin-top: -36px }
.toolbar-items { margin-top: -2px }

.private-browsing-indicator,
.tab-close-button,
.titlebar-spacer,
#forward-button, #back-button,
#tracking-protection-icon-container, #identity-icon-box, #identity-box,
#star-button-box,
#PanelUI-button,
#fullscreen-and-pointerlock-wrapper,
.titlebar-buttonbox-container
{ display: none }