We have a dedicated admin page (`/admin/customize/email_templates`) that lets admins customize all emails that Discourse sends to users. The way this page works is that it lists all translations strings that are used for emails, and the list of translation strings is currently hardcoded and hasn't been updated in years. We've had a number of new emails that Discourse sends, so we should add those templates to the list to let admins easily customize those templates.
Meta topic: https://meta.discourse.org/t/3-2-x-still-ignores-some-custom-email-templates/308203.
