For inserting a node between, 'Parent' and 'Child', there is only one way to do it. By 'Copy and Paste' method only.
To add a node in between, do this.
i. Add a new node 'Parent II' to 'Parent'
ii.Copy the node 'Child'. Then click on node, 'Parent II' and click 'Edit'->'Paste'
iii. Then click on initial node 'Child' again click 'Edit'->'Cut'
iv. Now you see you have a new 'Parent II' node to 'Child'.
The above mentioned method is not so difficult to follow. It is easy.