When I create a new domain with the virt-manager UI, I always have to "edit configuration before install" and edit the XML manually to apply specific configuration changes. This gets very tedious when creating 10s or 100s or VMs.

It would be better to edit the domain XML template once, however I have found nothing in the documentation referring to where this template is coming from or the appropriate way to edit it. I'm not even sure if it's virt-manager or libvirt that manages this template.