Any (sub)domain can be added to an environment. As long as the (sub)domain has an A-record pointing to Forest.host. Each domain will receive it’s own Letsencrypt certificate automatically.
DNS
Only domains with a DNS-records pointing to Forest can be added!
Make sure to add an A-record for your domain pointing to 45.135.56.67
Redirects
Adding a redirect is as easy as adding a domain and checking Redirect to another destination in the Add domain form. Next select the service the redirect needs to refer to.
Domain redirects can easily be added, the same way as a regular domain. First make sure the domain that needs to be redirected has a DNS-record pointing to Forest, see above.