Should be dropped between 2 nodes

[hungnguyen1412]

I mean, we have a tree likes that:
--node 1
--node 2
--node 3

I drag and drop the node 3 between node 1 and node 2, it becomes:
--node 1
--node 3
--node 2

Thanks

[minop1205]

Thank you for your comments.
This issue is currently being addressed, but will be closed as it overlaps with the following issue.
#41