Hello b thomas,
I hear what you're saying and I want to make sure you know your options. The steps I mentioned above for QuickBooks Desktop 2020 should only be sending one email to your customer with all of the invoices attached. If you're following those steps and it doesn't seem to be working, I recommend reaching out to support to troubleshoot with an agent. Check out the Intuit QuickBooks Desktop software support policies to learn how to reach that team.
If you have a version older than 2020, this option won't be available to you and I encourage you to consider one of the workarounds outlined earlier in the thread. You can also consider upgrading your version of QuickBooks to be able to take advantage of the newest features, such as being able to send multiple forms in a single email. A support agent would also be able to help you learn your options for upgrading, so don't hesitate to reach out!