Checkvist help/reference says:
Move list items
…
If you choose a list, the selected item will move to the top of that list. If you choose a list item, it will move below it, as a sibling.
In my experience, however, the moved item becomes the first child, not a sibling, of the chosen list item. In other words, regardless of whether the destination is a list or a list item, the item being moved becomes the top sub-item under that destination.
Am I not understanding the help/reference correctly?