How to assign teams to players?

Say you have 1,000 players on the same server. How would one go about assigning every player to their own “team”? So that an object will only appear for the player that interacted with it. For instance player 1 flips a lightswitch & this information is saved & stored on the server, and the lightswitch stays flipped for player 1. Player 2 did not flip the switch so they can’t see that it was flipped by player 1 & so it remains unflipped for player 2 and all the other players because player 1 was the only one that flipped it. Essentially there’d be 1,000 different “teams”, 1 for each player.
I’m using the Survival Game Kit which already includes some type of multiplayer functionality with saving of players & their inventories, but I’m very new to blueprints so I’m not sure if/how I could use a function/variable in it for this “team” function.

Anyone have any ideas?