userChrome.css

image.tab-close-button {
    display: none !important;
}

/* Remove the top margin Zen's own zen-tabs.css adds to #navigator-toolbox
   for macOS traffic-light space. That rule has high selector specificity
   (multiple :not()/attribute conditions), so the ID is repeated here to
   outweigh it rather than trying to match its exact condition chain. */
#navigator-toolbox#navigator-toolbox#navigator-toolbox {
  margin-top: 0px !important;
}

*|*:root[zen-compact-mode="false"] .titlebar-buttonbox {
  display: none !important;
}
.titlebar-buttonbox-container {
  display: none !important;
}

.zen-workspace-pinned-tabs-section {
  display: none !important;
}

/* Remove the fade-in transition on tooltips — ui.tooltipDelay only
   controls the wait before showing, not the appear animation itself */
tooltip {
  transition: none !important;
}

#urlbar:not([usertyping], [searchmode]) > .urlbarView {
  display: none !important;
}

#urlbar-results div.urlbarView-row[row-selectable][type="top_site"] {
  display: none !important;
}

#urlbar[zen-newtab="true"] {
  #identity-icon {
    list-style-image: url("chrome://browser/skin/zen-icons/new-tab-image.svg") !important;
    filter: opacity(0.5) !important;
  }

  &[open] #identity-icon-box::after {
    content: "New Tab" !important;
    filter: opacity(0.5) !important;
    padding-left: 6px !important;
  }
}

/* Animation smoothness: Quick Snap */
:root {
  --zen-animation-smoothness: all 0.15s cubic-bezier(0.175, 0.885, 0.3, 1.3),
    filter 0.15s ease-in-out, opacity 0.2s ease-in-out !important;
}

/* Tab switch animation */
#tabbrowser-tabpanels
  > hbox:not([zen-split="true"]):not(:has(.zen-glance-background)) {
  transition: var(--zen-animation-smoothness) !important;
  scale: 0.9 !important;
  opacity: 0;
}
#tabbrowser-tabpanels > hbox.deck-selected:not([zen-split="true"]) {
  scale: 1 !important;
  opacity: 1 !important;
}

/* URL bar zoom animation */
#browser:not(:has(.zen-glance-background)) #tabbrowser-tabpanels {
  transition: var(--zen-animation-smoothness) !important;
}

#browser:has(#urlbar[open][zen-floating-urlbar="true"]) #tabbrowser-tabpanels {
  pointer-events: none;
  scale: 1.1 !important;
  filter: blur(10px) brightness(70%) !important;
}

#urlbar[open][zen-floating-urlbar="true"] .urlbar-background {
  background-color: color-mix(in srgb, var(--zen-urlbar-background-base) 60%, transparent) !important;
  border-radius: 1em !important;
}

#urlbar-input,
.urlbar-input-container {
  text-align: center !important;
}

/* Take the left-side identity/lock icon out of flex flow so the text field
   spans the full bar width and centers relative to the whole bar, not just
   the space left over after the icon. Scoped to the floating urlbar only —
   applying this globally broke the icon position in the normal toolbar. */
#urlbar[open][zen-floating-urlbar="true"] #identity-box {
  position: absolute !important;
  left: 8px !important;
}

#urlbar-zoom-button {
  display: none !important;
}

.zen-current-workspace-indicator {
  display: none !important;
}

#urlbar-container[breakout="true"] {
  background: none !important;
  box-shadow: none !important;
  border: none !important;
}

.urlbar-background {
  background: none !important;
  box-shadow: none !important;
  border: none !important;
}

panel,
menupopup,
panelview,
panelmultiview,
.panel-arrowcontent,
#appMenu-popup,
#appMenu-popup panelview,
#appMenu-protonMainView,
#widget-overflow,
#customizationui-widget-panel {
  appearance: none !important;
  -moz-appearance: none !important;
  background: #000000 !important;
  background-color: #000000 !important;
  border-radius: 16px !important;
  color: #f2f2f2 !important;
  font-family: Verdana, sans-serif !important;
  font-size: 12px !important;
  font-weight: 400 !important;
  overflow: hidden !important;
  clip-path: inset(0 round 16px) !important;
}

.panel-viewstack,
.panel-subview-body,
.panel-header,
.panel-footer {
  background: transparent !important;
  border-radius: 16px !important;
}

toolbarbutton.subviewbutton:hover,
menu[_moz-menuactive="true"],
menuitem[_moz-menuactive="true"] {
  background-color: rgba(255, 255, 255, 0.12) !important;
  color: #ffffff !important;
}

panel toolbarbutton,
panel label,
panel description,
menupopup menu,
menupopup menuitem {
  font-family: Verdana, sans-serif !important;
  font-size: 12px !important;
  font-weight: 400 !important;
}

/* "site.com is now full screen / Exit Full Screen (esc)" banner */
#fullscreen-warning {
  background-color: #000000 !important;
  border-radius: 16px !important;
  border: none !important;
  font-family: Verdana, sans-serif !important;
  font-size: 13px !important;
  padding: 10px 16px !important;
}