DNS zones can be added manually or (preferrably) via DNS auto-discovery as discussed at: https://docs.device42.com/tools/setup-dns-autodiscovery/
To define a DNS Zone, add/edit the zone specific fields show above.
Why can’t I edit DNS records from within the DNS zone edit page?
Unlike other add/edit pages in device42 application, there are no editing option for DNS records from within the DNS Zone page. You can still edit the records from the records list page.
The reason for this is page rendering speed and CPU utilization. Unlike other records, a DNS zone can have thousands of records and the option to edit all of them at the same time increases the page load time significantly, so we have disable that option here.