Api to add new subdomain to amplify app .

There are some issues with the createDomainAssociation API that is provided by the AWS SDK amplify. I am not able to associate the subdomain to amplify the app using createDomainAssociation API. I Found another API to associate subdomain updateDomainAssociation. For using updateDomainAssociation API, there are concerns that this may negatively affect the already associated subdomains if the request fails.

Question: If there is an API that we can use to add the subdomain to the amplify app. Question: When using updateDomainAssociation, if we add already associated subdomains along with a new subdomain in the updateDomainAssociation API request, does this API re-associate all subdomains, or does this only update/add/remove whatever is there in the request.