This setting isn't compulsively.You can create a lobby for this duel system and the players will be teleported to here after finishing a game.
Commands
Command
Action
/dt lobby(l)
Teleport to the lobby
/dt lobby(l) set
Set the lobby
/dt lobby(l) remove
Delete the lobby
Quick sign
Players can open the searching opponent panel by the quick sign.The usage is as followed
Finish creating
If the language file you used it 'en_US',you can enter [1vs1 SEARCHING] in the first line to create it.To be sure,you can change this text in the language file.