I believe that in 8.1, the window size will get set to the "port on screen" values that you set for each room. But in studio, the window size is set to the "port on screen" you set in the first room and stays that way. So if you want your window size to be the same throughout the whole game (as you probably do), then just change the "port on screen" of the first room. If you want to change it dynamically, you can use the window_set_size function. I hope this is what you wanted; it's easy to confuse the terms view, port, window, size, etc.