I appreciate you checking the feature for combining multiple estimates in QuickBooks Desktop (QBDT), GreenhouseCH.

Adding multiple estimates to an invoice is currently unavailable in QBDT. In the meantime, you can add a single estimate to one invoice only. To do this, you need to enable the progressing invoice. Here's how:

1. Sign in to QuickBooks Desktop as an admin.
2. Go to the Edit menu and select Preferences.
3. Select Jobs & Estimates from the list of menus.
4. Select the Company Preferences tab.
5. Select "Yes" in the "Do You Create Estimates?" section, then select "Yes" in the "Do You Do Progress Invoicing?" section.
6. Select OK to save and close your preferences.

Once done, create an estimate and then apply the invoice. Follow steps 2 & 3 in this article to guide you further: Set up and send progress invoices.

I'd encourage you to send a product request to our engineering team so they can consider having this functionality in the upcoming updates.

Here's How:

1. Go to the Help menu and click Send feedback online.
2. Choose the Product suggestion.
3. Enter your comments and product suggestions, and click Send feedback to submit.

Moreover, I'll add this article to help you record your customer's payments: Record invoice payments.

Please let us know if you have other questions about the QuickBooks feature. We'll do our best to address them. Have a great day.