Assuming your peer comment is peer1 and the correct endpoint DNS record is peer1.mydomain.com, you can use this RouterOS script to update the endpoint based on the DNS record:
:if ([interface wireguard peers get number=[find comment=peer1] value-name=endpoint-address] != [resolve peer1.mydomain.com]) do={interface wireguard peers set number=[find comment=peer1] endpoint-address=[/resolve peer1.mydomain.com]}Related posts which might make that easier to understand: