vm hostname

Hello, I need to add several entries to the guest VM "DNS domain" using Proxmox. As result the guest VM hostname changes to the combined DNS domains name: The "DNS domain" field supposed to have only one "."-separated entry. Please advice how I can add several DNS domains in Proxmox WEB GUI.

I noticed with proxmox backup that if you have say 5 different proxmox hosts, and each one of those hosts have a vm/100 and are backed up to the proxmox backup server that they all show up under the same vm/100 Backup group, is there a way to separate them based on the host they're being backed...