Currently, tracking income in a single invoice while adding billable expense for multiple projects isn't possible, Allow me to explain this further, Lori.

QuickBooks Online (QBO) only tracks income when an invoice is generated for each project separately. You can create an invoice for each individual project to be able to track revenue accurately and be able to send invoice to your customer.  I've added screenshots for your reference:

Once you're able to create an invoice for each project, this will now track your income and will already show on the graph. 

QuickBooks provides a wide range of reports that can help you track your income and other financial data. You'll only have to ensure to filter them to show up the right information at the right place. I've added this article for more information: Customize Reports in QuickBooks Online.

Point out your comment below if you have any other concerns when tracking income on projects. We'll always be right here to help you anytime. Have a nice day!