Hello there, JWD2023. 

Your initiative and efforts to perform some workarounds are truly commendable. Let me give you some additional information to help you clarify your inquiries with regard to managing POS systems in QuickBooks Online (QBO).

Currently, QuickBooks Online (QBO) doesn't have a built-in option for connecting multiple cloud-based Point of Sale (POS) systems simultaneously, due to the complexity of managing data from multiple sources and potential conflicts. QBO focuses on single POS integration to maintain data integrity. 

While QBO has an API for custom integrations, restrictions may prevent multiple POS systems from writing data concurrently. Given these limitations, you are on the right track by manually entering data from multiple POS systems into QBO, allowing for immediate verification and error correction. 

Moreover, you can refer to this article to learn more information about integrating third-party services in QBO: Can QuickBooks Online directly integrate with third-party merchant services?

Furthermore, you can also read this article if you're encountering an error when trying to connect a third-party from QBO: Unable to connect an app from the QuickBooks Online app store

Should you have any other questions with connecting multiple systems in your account, you can always revisit this thread and click Reply to initiate another discussion. We're always here to help.