If someone were to look only at your title, they might guess the question is about how to tell whether a window is open or is minimized. That is not what your question turned out to be, but for the sake of anyone who happened to wander across this with that topic in mind:
You can tell whether a MATLAB figure is minimized by checking the figure WindowState property, which is 'minimized' if the window is minimized. If the window is open but docked then the WindowState will be 'docked'; if the window is open and not docked then the WindowState will be 'normal'
