Firefox multi-line tabs

userChrome.css

/* See imports from: https://github.com/MrOtherGuy/firefox-csshacks */
@import url(chrome/multi-row_tabs.css);

:root{
    --multirow-n-rows: 2;
    --multirow-tab-min-width: 170px;
}

/**
 * Style the Tab's closing icon
 */
.tabbrowser-tab:not([pinned]) .close-icon {
   fill: #c00 !important;
   border: solid 1px #ccc !important;
   display:-moz-box !important;
}

/**
 * Style the active tab 
 */
.tab-background[selected="true"] {
  background-color: #b6dbe3!important;
}