Good evening, @sf32158. 

Thanks for joining in on this thread. Also, it's great to see a new face here in the Community. 

I can help you add multiple estimates into one invoice in your QuickBooks Online account. To start, you'll have to create multiple estimates for your single client. Here's how:

1. Go to the + New menu.
2. Press Estimate.
3. Pick the name of your client.
4. Enter the necessary details.
5. Click on Save and New to create the other estimate.

Once done, we can combine the estimates into one invoice.

1. From the + New menu, select Invoice.
2. Choose the name of your client.
3. Locate the estimates in the pop-window, then click Add.
4. On the How much do you want to invoice? screen, choose which option works best for the transactions.
5. Hit Copy to invoice.
6. Once done, tap on Save and close.

Afterward, you can check out this guide about recording invoice payments.

I hope this helps. Feel free to reach back out if you have any other questions. Have a wonderful day and weekend ahead!