I have a solution that will help you use a QR code in your invoice @mscorporationx.
I'll guide you in the right direction so you can add a QR code to your invoices in no time.
Adding QR codes to customer invoices is not yet available in QuickBooks Online (QBO). I agree with Fiat Lux - ASIA that you may consider looking for a third-party application that supports the process at this time. This allows your customer to start paying you by scanning the barcode.
Once done, you can now use the app as soon as possible so your customer can pay you swiftly.
I've included some articles on how to upload sales templates and personalize them in QuickBooks:
If there's anything else I can do, do not hesitate to post here at any time. I'm always prepared to work with you again. Keep safe, mscorporationx.