How to hide/unhide a bunch of StaticMeshActors at once

an alternative is event dispatcher.
make an actor manager or even just use the player as the manager.

create an event dispatcher in player blueprint called “on show/hide” .

and then have the static mesh actors to get player at their begin play.

drag a line out from the player search for the dispatcher you just created in the player.bind an event to it.

player then can call the dispatcher with a button press or anything.
The actors will auto respond to the player