I plan to have this added into the next version of eSearch for WAB. Currently WAB does not even support centering the map based on a URL parameter.
Just pay attention to the actual url paramter in the example. It is not implying that you have to have a local folder url
My thoughts were to try this with the ParksFinder app since I'm assuming it's based on the same foundation as a WAB map. There is NO index.html to add that snippet to... and when I just drop the "?urlmodifiers" they give me quirky responses. I haven't tested with a WAB map yet, but I did get sketchy responses from our ParksFinder app we've set up.