In the launchers "Window"-menu, you will find an item named "Window Hierarchy". If you select this item, a crosshair cursor will show up, and ST/X waits for you to click on any smalltalk window on the screen.

After clicking, that windows widget hierarchy will be shown in a graphical inspector view.

You can further investigate the attributes of the widgets by selecting it in the tree and choosing one of the right-button popUp-menus functions.