We are actually interested in the exact same thing (sorry I can't provide a solution for you Claire McGinn)! We are looking at Web App Builder to create a report which would include attribute information, but more specifically information from the related table records (which is captured in the field using Collector).
The screening widget functionality would be perfect, if it would also include the related table records... I have also investigated creating a custom widget using the Report class, however I haven't been able to get this working on the related table the way we would like to. Another solution for us would be to be able to generate a report from the output of the Query Widget, which is in fact able to query on the related table. Although not ideal as it doesn't show the information of the related feature, it could also be a potential solution (but how to generate a report from the outcome of the Query Widget?).
Would be great if we would be able to get some Esri insight as to how to solve this challenge!
Kind regards,
Maud
