Safari-like Firefox UI (no tabs)

macOS-userChrome.css

:root {
  --tab-border-radius: 6px !important;
  --toolbarbutton-border-radius: 6px !important;
  --toolbarbutton-inner-padding: 6px !important;
}

toolbar {
  --toolbarbutton-inner-padding: 6px !important;
}

#titlebar {
  height: 52px !important;
}

#tabbrowser-tabs {
  display: none !important;
}

#TabsToolbar-customization-target {
  height: 100%;
}

#alltabs-button {
  margin-left: auto !important;
  margin-right: 4px !important;
  list-style-image: url(data:image/svg+xml;base64,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) !important;
}

#nav-bar {
  margin-top: -52px !important;
  margin-left: 66px !important;
  margin-right: 36px !important;
  height: 52px !important;
}

#nav-bar-customization-target {
  display: flex !important;
  align-items: center !important;
}

#urlbar-container {
  --urlbar-container-height: initial !important;
  padding: 0 !important;
  height: 28px !important;
  margin: initial !important;
  margin-inline-end: 5px !important;
}

#urlbar {
  top: 0px !important;
  bottom: 0px !important;
  height: 100% !important;
  min-height: initial !important;
}

#urlbar[breakout][breakout-extend] > #urlbar-input-container {
  height: 100% !important;
  padding: var(--urlbar-container-padding) !important;
}

#urlbar-background {
  display: block !important;
  position: absolute !important;
  inset: 0 !important;
  height: 28px !important;
}

#urlbar-input-container {
  --urlbar-container-padding: 3px !important;
}

.urlbar-page-action {
  align-items: center !important;
  justify-content: center !important;
  height: 100% !important;
}

.urlbarView {
  z-index: 9999 !important;
  background-color: #353535 !important;
  margin-top: 6px !important;
  border: 1px solid var(--toolbarbutton-active-background) !important;
  border-radius: var(--toolbarbutton-border-radius) !important;
}

#identity-box {
  width: calc(var(--urlbar-container-padding) * 2+28px) !important;
}

/* Hide firefox text in url bar when on firefox pages */
#identity-icon-label {
  display: none !important;
}

/* hide forward and back buttons */
#back-button,
#forward-button {
  display: none !important;
}

/* remove titlebar spacers at ech end */
.titlebar-spacer {
  display: none !important;
}

/* remove menu button */
#PanelUI-button {
  display: none !important;
}

#identity-icon-box {
  padding: initial !important;
  width: calc(28px - var(--urlbar-container-padding) * 2) !important;
  display: flex !important;
  align-items: center !important;
  justify-content: center !important;
}

#private-browsing-indicator-with-label {
  display: none;
}