Sorry for the late reply, @Will.S. Unfortunately, I had no success figuring these things out when I was trying to use the Power BI integration. I’d thought that setting Task Parent as blank would have sorted out the subtask issue, but it seems that Task Parent and Parent Task are two different things! I did read a post about development work on sections, so that they’ll be distinguishable from tasks, but there’s still no confirmed timeline:
I’m sad to say I gave up on the app and moved back to downloading everything to a Power BI desktop report. It’s much easier to control the data, and you can export custom fields, which are a major blindspot in the Power BI app.