Demo: CSS grid-column-start

<div class='grid-container'>
  <div class='grid-item item1'>Item 1</div>
  <div class='grid-item item2'>Item 2</div>
  <div class='grid-item item3'>Item 3</div>
  <div class='grid-item item4'>Item 4</div>
</div>

.grid-container {
  display: grid;
  grid-template-columns: repeat(3, 100px);
  grid-gap: 10px;
}

.grid-item {
  background-color: lightblue;
  padding: 20px;
  text-align: center;
}

.item2 {
  grid-column-start: 2;
  grid-column-end: 4;
}

.item3 {
  grid-column-start: 1;
  grid-column-end: 3;
}

// No JavaScript required for this demo