Mosquitto addOn - create a second user?

Configuration
2

Please format your code as described in the FAQ.
The documentation for the Mosquitto addon specifically says:

A list of local users that will be created with username and password. You don’t need to do this because you can use Home Assistant users too, without any configuration. If a local user is specifically desired:

So just create a User in Home Assistant, keeps it all in one place.
If for some reason, you really need local users, it’s a list, so:

logins:
  - username: myuser
    password: mypassword
  - username: myuser2
    password: mypassword2