The tool to set custom DNS doesn't allow more than one TXT record per subdomain, and gives an error. However, multiple TXT records for a single subdomain is valid and is required for Let's Encrypt's certbot DNS validation process e.g., when validating a naked domain and a wildcard.
Is there a way to work around this with Dynadot's name servers?
Thank you for your patience while we looked into this for you. We're happy to advise the feature has been added and you can now add more than one TXT record for the same subdomain.
Please let us know if you have any other questions.