You can use one of the following three methods when inserting a C1TreeViewNode in the designer:
Right-click on the C1TreeViewNode you wish to add a child node and select Insert Item | C1TreeViewNode.
Select the C1TreeViewNode you wish to add a child node and click on the Insert Item button's drop-down arrow and select C1TreeViewNode.
Select the C1TreeViewNode you wish to add a child node and click on the Edit menu and select Insert Item | C1TreeViewNode.