how to add mutiple domain name to existing AWS certificate

Hello,

I think it need to be done when you request a certificate , please see the below from Point no 2 (When you request a wild-card certificate...) https://docs.aws.amazon.com/acm/latest/userguide/gs-acm-request-public.html

I am not too sure if you can update an existing one with a wild-card domain name

Request a public certificate using the console

To request an ACM public certificate (console)

1. Sign in to the AWS Management Console and open the ACM console at https://console.aws.amazon.com/acm/home.
Choose Request a certificate.
In the Domain names section, type your domain name.

2. You can use a fully qualified domain name (FQDN), such as www.example.com, or a bare or apex domain name such as example.com. You can also use an asterisk (*) as a wild card in the leftmost position to protect several site names in the same domain. For example, *.example.com protects corp.example.com, and images.example.com. The wild-card name will appear in the Subject field and in the Subject Alternative Name extension of the ACM certificate.

When you request a wild-card certificate, the asterisk (*) must be in the leftmost position of the domain name and can protect only one subdomain level. For example, *.example.com can protect login.example.com, and test.example.com, but it cannot protect test.login.example.com. Also note that *.example.com protects only the subdomains of example.com, it does not protect the bare or apex domain (example.com). To protect both, see the next

SSL certificates are digitally signed so modifications to existing issued certificates are not possible. You can, however, create a new certificate request for the primary domain name and choose Add another name to this certificate to add additional names.

You can also request a new certificate for an additional domain and attach that new cert to your load balancer along side the existing certificate. Add certificates to the certificate list

Note: You cannot request certificates for Amazon-owned domain names such as my-load-balancer-1234567890abcdef.elb.us-east-2.amazonaws.com, you would need to request a certificate for a CNAME or alias record that points to your load balancer, Routing traffic to an ELB load balancer