Sharing a Blueprint solution that’s based on how Valley of the Ancient did it.
Unreal has since deprecated DataLayerSubsystem (it’s still there in 5.3) and replaced it with the DataLayerManager, whose SetDataLayerRuntimeState uses Data Layer Asset objects instead of Actor Data Layer structs. Because WorldPartitionStreamingQuerySource uses Data Layer names, it’s quite easy to get that from Actor Data Layer structs. We haven’t yet figured out how to get names from Data Layer Asset objects.
We’ve still yet to create an Async version of the SetDataLayerRuntimeState. The documentation on Data Layer functions from Unreal’s team is very, very lacking.