Thanks Robert. The extent was set from another app (workflow manager) and it's not zoomed in close enough for what I need.
If that's the case I would have pass other values to my url. How about query?
http://localhost/webappbuilder/apps/8/?query=???
I have many layers, no sub layers. If I need to pass a layer id in the URL, how do I find layer id ?
Many thanks.
Edit: I got the URL works! I do not need Layer id for my URL in this case. However I still do not know how to get to the webmap json.