I can't use eSearch because we are using AGOL rather than hosting Portal on our servers. The Query widget runs into 2 problems:
- The Query widget doesn't respect any filtering you have placed on the underlying web map (ESRI has logged this as a bug to, no date as to when a fix will be implemented); and
- You can only select one layer at a time, and I can already hear my users complaining about that.
However the geoprocessing service I'm looking at only needs the extent of all the features that have been selected. So I think that if I use the Draw tool, adding its output as an operational layer and use that as the input to the service, that will get me around the issue (there's a big "I think" in there).