Do the actors, that you want to “hide”, retain any “state” between activations? If not, consider just removing them and then recreating. Note that adding instanced actors at runtime isn’t quite supported yet. I did start work on it, so most of the stuff required for that is there, but some bits are still missing and you might need to add those yourself.
If they do retain a state, or just want to avoid creation cost (but don’t mind memory cost of keeping hidden actors around), you can force entities’ LOD off and disable LOD processing on them - `UInstancedActorsStationaryLODBatchProcessor::Execute` does something similar - things that switch between Batch- and Detailed-LOD get their tags modified to influence which processors will handle the modified entities.
Re making instanced actors change location: it’s not supported at the moment. But you can change locations of mass entities that are visualized with other visualizers. See CitySample for example how the moving vehicles and pedestrians are implemented.
Re working with Mass in multiplayer environment, one critical thing missing is Mass’s native replication. That’s why InstancedActors do their own replication.