1) It would be faster to initiate the invoice from the customer rather than leaving to go to the invoice tab and lookup the customer to start the invoice 2) From the invoice tab, after doing a limited number (1, up to 6) invoices, the customers are no longer pulling up to even be able to create an invoice. Now there is no work-around for this, so can't create a new invoice for other customers until log out, refresh, etc.. Having another way to generate invoices for customers would help.
Great news, this already exists! Once you have clicked into the customer record you will see tabs across the bottom, click on the history tab and then select which payment type you want to create for the customer. If you click the payment tab you will notice you can add a quick pay payment directly from this page, same is true of invoices and recurring plans when you have the invoice app installed and orders when you have the retail app installed. I've attached an image below to further help you locate this feature.