How can you add a child, to existing child

Say you have a tree, parent with children.  Click a child and some logic states child adds a child.  It appears that unless the child is created with folder = true, it won't add the child.

Is there a way to override this and turn a child into a parent with the folder designation ?

...

BTW - this is a great component - have not found any so far for SwiftUI and MacOS for a tree view !
