Now, I succeeded saving and recalling all actors transforms in a level using the SaveGame class.
However, if anyone ever stumbles upon this post again, one thing might be of interest:
Although the class “Actor” pretend to serializable via SaveGame-Class, it does NOT really serialize!
So one has to to serialize property-members manually, it is not possible to save an actor with all its properties right out of the box, unfortunately.
That’s a pitty, as discussed here too.
However, thank you very much.