iso-profiles-settings/tromjaro/gnome/desktop-overlay/etc/skel/.local/share/gnome-shell/extensions/unite@hardpixel.eu/themes/pop-dark/maximize.svg

<svg height="24" width="24" xmlns="http://www.w3.org/2000/svg">
  <path d="m8 8v8h8v-8zm2 2h4v4h-4z" fill="#ededed" opacity=".7"/>
</svg>