I'm not familiar with PowerBuilder but I have a task to create Automatic UI Test Application for PB. We've decided to do it in Python with pywinauto and iaccesible libraries. The problem is that some UI elements like newly added lists record can not be accesed from it (even inspect32 can't get it). 
Any ideas how to reach this elements and make them testable?
I'm experimenting with code for a tool for automating PowerBuilder-based GUIs as well. From what I can see, your best bet would be to use the PowerBuilder Native Interface (PBNI), and call PowerScript code from within your NVO.
If you like, feel free to send me an email (see my profile for my email address), I'd be interested in exchanging ideas about how to do this.
How to make PowerBuilder UI testing application?