The AnyWin, Control, and MoveableWin classes are logical (virtual) classes that do not correspond to any actual GUI objects, but instead define methods common to the classes that derive from them. This means that Silk Test Classic never records a declaration that has one of these classes.
Furthermore, you cannot extend or override logical classes. If you try to extend a logical class, by adding a method, property or data member to it, that method, property, or data member is not inherited by classes derived from the class. You will get a compilation error saying that the method, property, or data member is not defined for the window that tries to call it.
You can also not override the class, by rewriting existing methods, properties, or data members. Your modifications are not inherited by classes derived from the class.