This sounds very much like something I’d say and / or write.
This menu widget you’re trying to access:
Where is it created? Where the arrow is pointing? Could it be the Add to Viewport node hiding at the edge?
what cast to does
It’s a test + conversion. Here, you take an object reference of any type and test if it’s the object type that you want (you’re testing if the object you did not provide is a menu widget). If the test succeeds, the engine will allow you to use this object (as Menu) as if it was the object of the type you wanted.
This node in the middle is also casting:
We’re testing if the letter Q is an integer and then attempt to convert and use it as a digit. As you can imagine, this will not compute well. In both cases you need a value to test.
So, where is the menu widget?