I am unaware of how to create sub-processes on demo.bpmn.io. I can add a collapsed subprocess, or I can add an expanded subprocess, but I cannot seem to relate the two.
I have tried (double) clicking the [+] on the collapsed subprocess, but that leads me to revise the text. I think this might be similar to the thread here.
Thanks for the response nikku. The three points you mentioned were exactly what I was asking for. Also, my understanding that the difference between an Activity and a subprocess is that a subprocess is special because it’s reusable / callable from anywhere.