Hi pete-willers-sec,
Thanks for joining us here on the community!
When entering an invoice, only a product/service can be selected, and this is linked to a Chart of Account by the income account selected on the P/S itself - the sales account you're currently seeing when entering an invoice will be the default 'sales' service set up by QuickBooks.
You can create or view products/services by going to Sales > Products and services, and then select edit to view the details and field for income account.
Thanks :)