Two mosquitto servers with separate passwords

Here’s my configuration:

  1. gateway, gateway-bridge, and mosquitto (as a bridge) running on a Raspberry Pi
  2. Other components on a remote Ubuntu box, including the remote mosquitto server

I see how to set the MQTT IP, user name, and password for the remote mosquitto server and put them in the toml file

What I don’t see is how to set a user name and password for the LOCAL mosquitto server (i.e., the one used by the gateway-bridge on the Pi), other than in the yml file.

What I’m asking is if there is a way to set two different IDs and passwords, one pair for each of the local and mosquitto servers. One could (and still can) do that in the yml file, but I don’t see a way to do it in the toml file