Each node in the frame tree is a tree node object (yeah, really). All internal tree nodes have a :parent property and a :children property. As an example, we can inspect the root node in the REPL:
(def node (get-in jwno/context [:window-manager :root]))
(def parent (in node :parent))
(def children (in node :children))
(printf "Parent: %n, number of children: %n" parent (length children))Since it's the root node, its :parent is nil. And the :children property is a simple array, where you can have access to all its child nodes.
The tree-node-dump-subtree function in win.janet is a good reference for traversing the frame tree recursively (It's the implementation of the :dump-subtree method we used to print the frame tree in Inspecting the Frame Tree).