How can i create Panels with Window Affordances (or equivalent functionality)

Meta's Horizon OS provides so called Window Affordances like the edge and resize handles.

I have been so far unable to implement functionality inside an Meta Spatial SDK using android app. Marking a panel Grabbable in Meta Spatial Editor gives the ability to move it but doing so feels more difficult then with native windows.

I have not found a way to make resizeable panels in a custom app yet. Even Meta's own applications like "Focus" aren't providing that functionality.