You can use the 'windowMenu' style attribute to achieve what you are looking for:
https://4js.com/techdocs/genero/fgl/devel/DocRoot/User/PresentationStyles.html#STYATT_MDIWith this MDI style attribute you have a list of child programs in the current parent MDI container, be able to display them in cascade or tile mode, put the focus on a given one...
I've attached a simple test case to give you an overall idea.
Best regards.