I'll point you out to the right direction for the support, @RichardH.
First off, I appreciate the amount of effort you've exerted so far. I recommend contacting your 3rd party app support. This way, they can provide you with a step-by-step process.
As the previous agent suggested, performing this in the test file won't affect any of the data that you currently have. The purpose of this is to verify and understand the process.
You might also want to give this article a visit. Itβs about how to change product and service items types in QuickBooks Online.
Let me know if you need further assistance with your QuickBooks-related concerns. I'd be more willing to to help you. Keep safe!
