macos-native-tabbar.css

/* ------------------------------------ */
/* Firefox Translucent Tabbar for macOS */
/* ------------------------------------ */

:root:not(:-moz-window-inactive) #navigator-toolbox {
   background-color: transparent !important;
}

:root #TabsToolbar,
:root #titlebar,
:root #tabbrowser-tabs,
:root #nav-bar,
:root #PersonalToolbar {
   -moz-appearance: -moz-mac-vibrant-titlebar-light !important;
   -moz-appearance: -moz-mac-source-list !important;
   background-color: transparent !important;
}

/* De-emphasize tab icons and names when window is unfocused */
:root:-moz-window-inactive .tab-content {
   opacity: 0.6;
}

/* recolor toolbar button hover/active bg colors to semi-transparent */
:root {
   --toolbarbutton-hover-background: color-mix(in srgb, currentColor 11%, transparent) !important;
   --toolbarbutton-active-background: color-mix(in srgb, currentColor 21%, transparent) !important;
}

/* make tabs toolbar translucent */
/* FF 99 > lwthemetextcolor="bright" */
/* FF 100< lwt-default-theme-in-dark-mode="true" */
:root:not(:-moz-window-inactive [lwt-default-theme-in-dark-mode]) #TabsToolbar {
   -moz-appearance: -moz-mac-vibrant-titlebar-light !important;
   -moz-appearance: -moz-mac-source-list !important;
}

:root:not(:-moz-window-inactive)[lwt-default-theme-in-dark-mode] #TabsToolbar {
   -moz-appearance: -moz-mac-vibrant-titlebar-dark !important;
   -moz-appearance: -moz-mac-source-list !important;
}

:root:-moz-window-inactive[lwt-default-theme-in-dark-mode] {
   --lwt-accent-color-inactive: rgb(40, 40, 40) !important;
}

:root:not([lwt-default-theme-in-dark-mode]) .tabbrowser-tab:not([selected="true"]) {
   color: #000 !important;
}

:root[lwt-default-theme-in-dark-mode] {
   --tab-line-color: hsla(280, 30%, 80%, 0.9) !important;
}