Tree widgets behave slightly differently depending on whether their parent widget is a base widget or another tree widget:

• If the tree widget’s Parent is a base widget, the tree widget becomes the root of a new tree widget hierarchy. The tree widget itself is not displayed, but it becomes the parent widget for other tree widgets that are displayed. This type of tree widget is referred to as a root node. Note that a tree widget that is a root node cannot be the parent widget for any widget except another tree widget.
• If the tree widget’s Parent is an existing tree widget, the new tree widget becomes a branchnode or leaf node in the existing tree widget. In this case:
• If the FOLDER keyword to WIDGET_TREE is present, the node becomes a branch node. Tree widgets that are branch nodes can become the parent widget of other tree widgets (but not of any other type of widget).
• If the FOLDER keyword to WIDGET_TREE is not present, the node becomes a leaf node. Leaf nodes cannot serve as the parent widget for any other widget.