chill-skeleton-basic/docker/pgadmin4/servers.json

{
  "Servers": {
    "1": {
      "Name": "Default",
      "Group": "Default group",
      "Port": 5432,
      "Username": "postgres",
      "Host": "db",
      "MaintenanceDB": "postgres",
      "SSLMode": "prefer"
    }
  }
}