Hi Alidoost,
Only the selected element in the Model Explorer will be visualized in the diagram when you drop them, that means in order to include the child elements, you need to also select them individually.
The pool can also has its lanes visualized when you selected the lanes and drop them together. However, you can show the lanes afterwards using the “show lane” function as shown in a previous post:
https://forums.visual-paradigm.com/t/bpmn-how-to-create-a-master-lane/13610/3?u=antony
Hope this helps,
Antony.
