Receiving emails on a Google domains subdomain

I purchased a domain from Google Domains, say, mydomain.tld. I do not plan to have any hosting/content on this domain as of now. I’m not using any external services or providers, just Google Domains and GMail.

I added the alias hello to my email forwarding settings in Google Domains. Now, any emails sent to hello@mydomain.tld get forwarded to my own GMail address.

Instead, I would like to use a subdomain for my alias, such as hello@abc.mydomain.tld (note the extra abc subdomain).

How can I configure MX records or other DNS entries in Google Domains to enable this?