tree-style-tab_custom.css

/* Push tab labels slightly to the right so they're completely hidden in collapsed state */
.tab .twisty {
    visibility: hidden;
    margin-left: -12px;
}

/* Hide close buttons on tabs. */
.tab:not(:hover) .closebox {
  display: none;
}

/* Show title of unread tabs with red and italic font */
.tab.unread .label {
  font-style: italic !important;
}


/* Improve positioning of tab labels */
.tab .label {
  margin-top: 6px;
}

/* Hide the "new tab" button */
.newtab-button-box {
  display: none;
}
#tabbar {
  bottom: 0 !important; /* Eliminate dead space on bottom */
}

/* Add private browsing indicator per tab */
.tab.private-browsing .label:before {
  content: "🕶";
}

/* todo
.tab.pinned {
  margin-top: -4px;
  min-height: 32px !important;
  height: 32px !important;
}
*/

/* Show internal tab id in the debug mode */
:root.debug .tab:not(.faviconized)::after {
  content: attr(data-tab-id);
  opacity: 0.5;
}