Selector or xpath of main content which need to insert, you can let it to be a array to contains multiple page elements. You may leave it empty because it will be generated automatically.
"pageElement": [ ".Context1>.Article", ".Context2>.Article", ".Context3>.Article" ]
When there are multiple nextLinks and multiple pageElements on one page, you can use a array to include all of them. And switch them by click "switch next link".