1 player game matchmaking lobby

I wanna make 1 player game matchmaking lobby where player can practice until they queue up for 4 player match by pressing some button.
4 player match should be a separate game.
They should always be able to cancel matchmaking or reject found game to stay in practice game by pressing some button.

What would be most optimal and clean way to do this?

This method is not yet possible because there is a chance that 8 players will enter at the same time and they will be different players. But you can do every minute of the pickup if there is then block the task for 1 minute until all players transfer and this needs to be implemented by the creator

I'm currently just a beginner, but I think you should take a look at ConcurrentStorage / SharedStorage for match making between game instances.

After that you can use TransferPlayersToGame to move them to your 4 player map.