1. Log into Intuit Link for Accountants;
2. Click on Firm Settings on the left panel;
3. Click on the Email Templates tab on the dashboard; and
4. Edit your existing template or create a new one.

If you send your organizers from 2019 Lacerte, I'm not sure if the changes you make to email templates there will flow through.  You can certainly give that a try.  But if you initiate the process within Intuit Link, your changes will definitely be reflected.