ass="hidden" style="grid-area: 3/4">0 0</item>
</grid>

<grid>
  <item>1</item>
  <item>2 2</item>
  <item style="grid-row: span 2">3 3</item>
  <item>4</item>
  <item style="width:6ch; grid-area: 3/1/4/5">5 5</item>

  <item class="hidden" style="grid-area: 3/4">0 0</item>
</grid>

<grid>
  <item>1</item>
  <item>2 2</item>
  <item style="grid-row: span 2">3 3</item>
  <item>4</item>
  <item style="width:6ch; grid-area: 3/1/4/4">5 5</item>

  <item class="hidden" style="grid-area: 3/4">0 0</item>
  <item c