I'm trying to draw a BPMN process flow. I want to include a sub-process. I dragged a sub-process to the working area. I've tried dragging other tasks, etc. on top of it. However, they aren't included in the sub-process. In other words, when I select and move the sub-process, they are left behind to fend for themselves.
I see the yEd grouping capability but that isn't BPMN. I'm trying to stick to BPMN only symbols.