I am not sure if that is supposed to work, I am especially confused by what you mean by ‘dragging’ in this context. Do you want an Actor/Object variable that can only be assigned a value if that Actor/Object implements a certain Interface? What I would try to do is using an Actor or Object type variable and checking in the ConstructionScript if it implements ‘MyInterface’. If not, I set the variable to null.
Something like this:
