Parenting allows UI elements to be positioned and sized according to other UI elements. Parenting hierarchies can go many levels deep and the parent/child relationship can be visualized by the white line connecting the parent to the child when the child is selected.
To change the parent/child relationship in the tree view:
Select a child
Drag+drop the child onto the desired parent
The child can be detached from its parent by drag+dropping it onto the Component.
Drag+dropping onto a parent may set the Parent property to an instance inside of the parent's Component type sets its Default Child Container value. For more information see the Default Child Container page.
To set a parent/child relationship:
Select the child
Change the Parent property to the desired parent: