2 tanks, 1 healer, 2 dd, 1 sniper

Hello. I tried to understand how the “workshop” works. I didn’t understand anything. I wanted to create a special game mode. Each team of players can choose 2 tanks, 1 healer and 3 dd. Only 1 dd can be a “sniper” (Hanzo Ash or Widow). It would be great if someone can and wants to create this game mode. Tell me if you do something like that=). Thanks.