<div id="sortable-multi-1-1" data-mdb-sortable-init class="sortable-list d-flex align-items-start" data-mdb-item-class="sortable-item-nested">

  <div id="sortable-multi-2-2" class="sortable-item-nested" data-mdb-connected-list="#sortable-multi-2-1" data-mdb-drag-handle=".drag-handler">

    <h4 class="text-center pt-2 drag-handler">To do</h4>

    <div class="sortable-item">Item 1</div>

    <div class="sortable-item">Item 2</div>

    <div class="sortable-item">Item 3</div>

    <div class="sortable-item">Item 4</div>

    <div class="sortable-item">Item 5</div>

  </div>

​

  <div id="sortable-multi-2-1" data-mdb-sortable-init class="sortable-item-nested" data-mdb-connected-list="#sortable-multi-2-2" data-mdb-drag-handle=".drag-handler">

    <h4 class="text-center pt-2 drag-handler">Done</h4>

    <div class="sortable-item">item 6</div>

    <div class="sortable-item">item 7</div>

    <div class="sortable-item">item 8</div>

    <div class="sortable-item">item 9</div>

  </div>

</div>