Thanks for providing us the detailed information of your concern, @Bob M.
The option to add a customer name to the subject field in the email template is currently not possible in QuickBooks Desktop (QBDT). I see how this feature could benefit you and other users.
I'll submit this feature request on your behalf to our product engineers so they'll consider adding this in the future.
In the meantime, you can consider the workaround suggested by my colleague JonpriL above.
Also, to know the latest news and updates on what's coming in QuickBooks, you can always visit our Product Updates page for reference.
As always, keep me posted if you have other concerns or questions. I'm always here to help.
