firefox/imports/centered_tab_content.css

/* Source file https://github.com/MrOtherGuy/firefox-csshacks/tree/master/chrome/centered_tab_content.css made available under Mozilla Public License v. 2.0
See the above repository for updates as well as full license text. */
.tabbrowser-tab[selected]:not(:hover):not([pinned]) .tab-label-container,
#tabbrowser-tabs:not([closebuttons="activetab"]) .tabbrowser-tab:not(:hover):not([pinned]) .tab-label-container{
  padding-inline-end: 6px !important;
}
.tab-icon-stack{
  margin-inline-start: auto
}
.tab-label-container{
  max-width: min-content;
  margin-inline-end: auto;
}