Top shows data after import.

Second shows removal of duplicate parents and 'Link as Child'

Third shows what happens when you try to adjust the tree manually

The solution is to 'Snap to the Grid' (Ctrl+A & press G) when the parent child link can be set vertical and then will move with the child.

Is it possible to add the grid snap to the Open/Import routine? I use this quite a lot and probably forget to do this initially about half of the time.