Let me help you generate a proforma invoice in QuickBooks Online (QBO), info-sociosolar.
A Proforma Invoice is usually used when exporting products, to confirm the details of the products to be ordered, and request a split deposit/balance payment from the buyer.
You'll be glad to know that QBO + IncoDocs integration has been added to the app store. You can connect to IncoDocs and instantly sync Invoices and Purchase Orders without re-typing any information.
You can also contact the IncoDocs support via phone or email. Simply look under the App information to get the details. They can help you connect with the app to your QBO account.
Also, a Proforma invoice is a non-posting form. In QBO, there isn't a separate Pro-Forma form template. However, you can use an Estimate Custom Form Style to create a Pro-Forma Invoice for your customers.