Good day, @jroneill.
For now, the option to change bill payment stubs to ACH is unavailable in QuickBooks Desktop (QBDT).
Once you record a bill payment, the only available payment method is check, credit card, and bank payment.
As a workaround, you can add the ACH info in your reference number when creating a bill. That way, it would reflect when printing the bill payment. Simply open your bill and add this info. Please see the screenshot below for your reference.

I can see how this option would help you in handling your transactions in QuickBooks. Thus, I'll take note of this as a suggestion to improve your experience in QBDT.
You can also send feedback to our developers. They can review your request and might include it in future updates. Here's how:
- Go to Help and select Send Feedback Online.
- Click Product Suggestion.
- Enter your suggestions and click Send Feedback.

Need help reconciling your accounts and closing out the current period? Check out this article if you need a guide: Reconcile an account in QuickBooks Desktop.
Do you have more questions about recording your transactions? Or do you need help with a specific task? Let me know and I'll keep an eye out for your reply. I'll see you soon.