I always do it in code after the child nodes have been added.
Code:
Dim rootNode as Node

With TreeView1

  Set rootNode = .Add(, , "root", "Root 1")
  .Add "root", TvwNodeRelationshipChild, "ch1", "Child 1"
  .Add "root", TvwNodeRelationshipChild, "ch2", "Child 2"
 
   rootNode.Expanded = True
End With