nixos-configs/home/firefox/custom.css

.browser-toolbar > * #alltabs-button,
#appMenu-fxa-status2,
#appMenu-fxa-separator {
  display: none !important;
}

:root * {
  --margin-left-icons-personal: 3px !important;
  --tab-height-personal: 40px !important;
  --uc-tab-corner-height: 41px !important;
  --uc-vertical-toolbar-width: 46px !important;
}

/* https://github.com/Godiesc/firefox-gx/blob/main/Tricks/README.md */
/* Extensions button into the "left-sidebar" - Immovable */

:root:not([chromehidden~="toolbar"],[sizemode="fullscreen"]) #PersonalToolbar {
  --padding-top-left-sidebar: 110px !important; /* 182px to one-line config */
}

:root:not([chromehidden~="toolbar"], [sizemode="fullscreen"]) #unified-extensions-button {
  --toolbarbutton-hover-background: transparent !important;
  --toolbarbutton-active-background: transparent !important;
  position: fixed;
  display: flex;
  top: 42px !important;
  left: 2px !important;
  z-index: 2 !important;
  fill: var(--general-color) !important;
  width: calc(var(--uc-vertical-toolbar-width) - 4px) !important;
}

:root:not([chromehidden~="toolbar"], [sizemode="fullscreen"]) #unified-extensions-button:hover,
:root:not([chromehidden~="toolbar"], [sizemode="fullscreen"]) #unified-extensions-button[open] {
  transform: scale(1.12) !important;
  transition: ease-in-out !important;
}

:root:not([chromehidden~="toolbar"], [sizemode="fullscreen"]) #unified-extensions-button:active {
  transform: scale(1.0) !important;
  transition-duration: 0ms !important;
}

#appMenu-addon-installed-notification,
#notification-popup {
  margin-top: -1px !important;
  margin-inline: -505px !important;
}

#customizationui-widget-panel {
  margin-top: -1px !important;
  margin-inline: -200px !important;
}

#PersonalToolbar .toolbarbutton-1 {
  margin-block: 0px !important;
}
#PersonalToolbar #PlacesToolbarItems > .bookmark-item {
  margin-block: 6px !important;
}

/* -------------------------------------------------------------- */
/* Fix menu */
:root:not([chromehidden~="toolbar"], [sizemode="fullscreen"]) #PanelUI-menu-button, :root[sizemode="maximized"] #appMenu-popup,
:root[sizemode="maximized"] #appMenu-popup {
  --tab-height-personal: unset !important;
}

:root:not([chromehidden~="toolbar"])[sizemode="maximized"] #appMenu-popup > panelmultiview > box > box > panelview {
  padding-top: unset !important;
}

/* Hamburger menu width */
:root:not([chromehidden~="toolbar"], [sizemode="fullscreen"]):is([sizemode="maximized"]) #PanelUI-menu-button[open] > stack,
:root:not([chromehidden~="toolbar"]) #PanelUI-menu-button .toolbarbutton-badge-stack {
  min-width: 46px !important;
}
toolbar .toolbarbutton-1 > .toolbarbutton-badge-stack {
  padding: 10px !important;
}

:root:not([chromehidden~="toolbar"]) #PanelUI-menu-button[open] > .toolbarbutton-badge-stack {
  width: unset !important;
}

:root[sizemode="maximized"]:not([chromehidden~="toolbar"]) #appMenu-popup panelview {
  width: unset !important;
}

:root:not([chromehidden~="toolbar"]) #PanelUI-menu-button > stack{
  display: unset;
  align-items: unset !important;
}

:root:not([chromehidden~="toolbar"]) #PanelUI-menu-button>stack::after {
  width: unset !important;
  content: unset;
  color: unset !important;
  padding-inline-start: unset !important;
  padding-block: unset !important;
  text-shadow: unset !important;
}

:root:not([chromehidden~="toolbar"])[sizemode="maximized"] #appMenu-popup {
  appearance: unset !important;
  margin-top: -1px !important;
  clip-path: unset;
  --arrowpanel-menuitem-padding: unset !important;
}

:root:is([sizemode="maximized"]):not([tabsintitlebar], [chromehidden~="toolbar"]) #appMenu-popup {
  margin-top: unset !important;
}

.subviewbutton:is(#appMenu-popup toolbarbutton):not(.subviewbutton-back) {
  padding-inline-start: unset !important;
}
.subviewbutton:not(.subviewbutton-iconic, .toolbarbutton-text, [checked="true"])>.toolbarbutton-icon, .syncNowBtn {
  width: unset;
  height: unset;
  margin-inline-end: unset !important;
}

#appMenu-zoom-controls{
  padding-inline-start: unset !important;
}

#appMenu-fxa-status2:not([fxastatus])>#appMenu-fxa-label2 {
  margin-inline-end: unset !important;
}

:root:not([chromehidden~="toolbar"])[sizemode="maximized"] #appMenu-fxa-status2 {
  padding-top: unset !important;
  border-image: unset !important;
  border-top: unset !important;
}

:root:is([sizemode="normal"], [sizemode="fullscreen"]) #appMenu-fxa-label2 {
  margin-inline-start: unset !important;
}

#appMenu-fxa-status2:not([fxastatus="signedin"]) {
  margin-inline-end: unset !important;
  margin-inline-start: unset !important;
}
#appMenu-fxa-status2:not([fxastatus="signedin"]):hover toolbarbutton {
  background-color: unset !important;
}

:root:not([chromehidden~="toolbar"])[sizemode="maximized"] #appMenu-popup {
  --arrowpanel-menuitem-padding: unset !important;
}