Thank you for getting back here, @Lori M.

Currently, the option to have a template with a different email message when sending invoices is unavailable in QuickBooks Online (QBO). As a workaround, you can use your saved word documents with different email messages and import them in QBO. For the instructions, please refer to the steps outlined by my colleague, Joesem M. 

For additional info about modifying and personalizing your sales form, see this article: Customize invoices, estimates, and sales receipts in QuickBooks Online. 

Also, if you have customers you invoiced regularly, you may consider reading this article to help you set up recurring invoices that can be sent automatically to them: How to create a recurring invoice and manage recurring transactions. 

Please let me know if I can be of additional assistance or should you have any follow up questions about creating templates in QBO. I’ll be here to help. Have a good one.