firefox css

/* ==========================================================================
   1. HIDE DEFAULT TABS TOOLBAR & WINDOW CONTROLS
   ========================================================================== */
#TabsToolbar:not([customizing]) {
  visibility: collapse !important;
}

#nav-bar .titlebar-buttonbox-container {
  display: flex !important;
  visibility: visible !important;
}


/* ==========================================================================
   2. COLLAPSIBLE OVERLAY SIDEBAR & HIDE SIDEBAR HEADER / CLOSE BUTTON
   ========================================================================== */
:root {
  --sidebar-min-width: 40px;
  --sidebar-visible-width: 210px;
  --sidebar-hide-delay: 60ms;
  --transition-duration: 100ms;
  --transition-type: ease;
  --z-index-sidebar: 100;
}

/* Hides Firefox's native sidebar title header and close 'X' button */
#sidebar-box #sidebar-header,
#sidebar-panel-header {
  display: none !important;
}

#sidebar-box {
  background-color: var(--toolbar-bgcolor) !important;
  position: absolute !important;
  top: 0;
  bottom: 0;
  left: 0;
  min-width: var(--sidebar-min-width) !important;
  width: var(--sidebar-min-width) !important;
  max-width: var(--sidebar-visible-width) !important;
  z-index: var(--z-index-sidebar) !important;
  transition: min-width var(--transition-duration) var(--transition-type) var(--sidebar-hide-delay) !important;

  /* Remove gray lines and rounded corners */
  border: none !important;
  outline: none !important;
  box-shadow: none !important;
  border-radius: 0 !important;
}

#sidebar {
  min-width: var(--sidebar-min-width) !important;
  width: var(--sidebar-min-width) !important;
  transition: min-width var(--transition-duration) var(--transition-type) var(--sidebar-hide-delay) !important;
  will-change: min-width;

  /* Remove gray lines and rounded corners */
  border: none !important;
  outline: none !important;
  box-shadow: none !important;
  border-radius: 0 !important;
}

#sidebar-box:hover {
  min-width: var(--sidebar-visible-width) !important;
  width: var(--sidebar-visible-width) !important;
  transition-delay: 0ms !important;
}

#sidebar-box:hover > #sidebar,
#sidebar-box:hover > .sidebar-browser-stack > #sidebar {
  min-width: var(--sidebar-visible-width) !important;
  width: var(--sidebar-visible-width) !important;
  transition-delay: 0ms !important;
}

#appcontent {
  margin-left: var(--sidebar-min-width) !important;
  border-radius: 0 !important;
}

#sidebar-splitter {
  display: none !important;
  min-width: 0 !important;
  width: 0 !important;
  border: none !important;
  background-color: transparent !important;
}


/* ==========================================================================
   3. AUTO-HIDING BOOKMARKS BAR
   ========================================================================== */
#PersonalToolbar {
  --uc-bm-height: 20px;
  --uc-bm-padding: 4px;
  --uc-autohide-toolbar-delay: 60ms;
  margin-left: 40px !important; /* Clears the collapsed sidebar icon strip */
}

:root[uidensity="touch"] #PersonalToolbar {
  --uc-bm-padding: 7px;
}

#PersonalToolbar:not([customizing]) {
  position: relative !important;
  margin-bottom: calc(-1px - var(--uc-bm-height) - 2 * var(--uc-bm-padding)) !important;
  transform: rotateX(90deg);
  transform-origin: top;
  transition: transform 135ms linear var(--uc-autohide-toolbar-delay) !important;
  z-index: 5 !important;
  background: inherit !important;
  background-color: var(--toolbar-bgcolor, #131317) !important;
}

#PlacesToolbarItems > .bookmark-item,
#OtherBookmarks,
#PersonalToolbar > #import-button {
  padding-block: var(--uc-bm-padding) !important;
}

/* Reliable hover and focus triggers across the whole toolbox area */
#navigator-toolbox:is(:hover, :focus-within) #PersonalToolbar {
  transition-delay: 100ms !important;
  transform: rotateX(0deg) !important;
}

#navigator-toolbox {
  --browser-area-z-index-toolbox: 4;
  overflow: visible !important;
  border-top-left-radius: 0 !important;
  border-radius: 0 !important;
}

#browser {
  border-radius: 0 !important;
}