In #1 I was referring to the following. The first image is after placing an instance of the blueprint in the level. The second is after using the transform widget to move the MyScene component.
Note that if I edit Location under Grab Point Offset, the blue diamond position will change while the widget stays in place. If the UPROPERTY is marked as EditDefaultsOnly, GrabPointOffset does not show in the details panel, but the transform widget is still able to move the MyScene component.