Someone might have a better suggestion but as far as my knowledge stretches I’d create a saveGame object and save all the data in there (monsters would be an array of types and another array of their transforms etc). It sounds like you’ve already familiarized yourself with these things probably but that’s how I’d do it. You’d then have to obviously create functionality that runs through the sameGame object and places the actors once a game has been loaded.
Hope that helps somewhat.