I can’t help with your exact issue. The best way I have learned is to first trace the steps you want to reproduce in the BPM. This isn’t exactly what you want, but some of it might help.
In my case I wanted to create a new line/release. So I opened the sales order entry form, navigated to my sales order. Then I started the tracer in Epicor. Go back to sales order form and create the new line/release. Go back to the tracer and stop the trace, and open the trace file.