Title. Is it possible? If so how? Currently I have a main menu widget that contains graphic settings and I also have a pause menu widget. Do I need to copy the functions and stuff I have to the pause menu widget or can it simply be cast to the new widget? Any help is appreciated. Thanks! 
Casting is not magic, it will not change one widget into another.
Judging by your example, you probably do not need casting at all. You simply need to access one widget from another - is that right?
Can you tell in which blueprint those widgets are created?