title: add a node to specific child node
body: <p>I can add a node to a treeview add method.But I want to add a node to specific child node.
  For example want to add a node to node5 </p>
  
  <pre><code>|___node0
  |___node1     
  |     |___node3
  |     |___node4
  |           |___node5
  |___node2
  </code></pre>
  
  <p>How do I can do this?
  Thanks.</p>