I appreciate you for sharing this information, @BradC13. Let me help you customize forms in QuickBooks Online (QBO). 

Since this feature is unavailable in QuickBooks, I recommend sending feedback to add this in future updates. If you have any suggestions or ideas, please follow these steps to send us your input:

1. Go to the Gear icon.
2. Select Feedback.
3. Type in your recommendation in the Share your feedback field.
4. Click Next.

In the meantime, we can create a new Quote transaction and add another line item by following these steps:

1. Login to your QBO account.
2. Click + New icon, and select Quote.
3. Enter the details in the required fields.
4. In the Products and services section, choose an Item in the first line.
5. In the second line, enter a space only in the Product and services section, and clear the amount in the quantity section before adding another line item in the third line.

Also, you can do the same steps when creating an Invoice transaction.

Moreover, you can check this article to learn how to set up your print settings so you can print checks in QBO: Configure your print settings for printing checks in QuickBooks Online.

We're always here to help if you have other feature concerns or need further assistance managing Quotes and Invoices in QBO. Don't hesitate to leave a reply in the comment section. Keep safe.