Version: Sage CRM 2018 R3

We created a custom entity for a client but at the time there was no expected need for a library or templates. The business practice has changed and we now need to add mail merge capability to the existing custom entity. Other than creating the new ASP pages (I can generate and copy the pages using the wizard in a test environment) and a new mail merge view, what has to be done to the entity to implement the mail merge process? Particularly wondering what table/metadata changes are required.