How to implement a marker line in jstree v.3 dnd (drag n drop)

[ghost]

I'm not really sure how the dnd operation works in jstree v3 (as in what makes the node inserted above or below the node and so on), but in v1, there seemed to be a marker line (jstree-marker-line) indicating where to insert the dragged-and-dropped node, but that has been discontinued and is no longer in v.3.