#tabs-newtab-button > .toolbarbutton-icon {
  margin-left: 1px;

  /* Origianl: calc((var(--tab-min-height) - 16px) / 2) = 10px */
  --toolbarbutton-inner-padding: 6px;
}
:root[uidensity="compact"] #tabs-newtab-button > .toolbarbutton-icon {
  --toolbarbutton-inner-padding: 4px; /* Photon: 6px */
}
:root[uidensity="touch"] #tabs-newtab-button > .toolbarbutton-icon {
  --toolbarbutton-inner-padding: 9px; /* Photon: 9px */
}