Expanding cert for additional domains under nginx

I want to expand a certificate to include a few more domains

certbot --expand -d domain.com, domain1.com, domain2.com etc
If im on cloudflare but only using DNS (not caching) and not using SSL on CF, do i need to add anything else?

What happens if this fails, its a high traffic site hosting the certificates, i need to put them on one cert because of a redirect and its causing invalid cert error in browser

A post was merged into an existing topic: Adding different domains to existing certificate?