Hi. I'm noticing a small bug (I think) with the WAB filter widget. I have the widget set up with a couple filters and it works fine, but references to fields are using the field name rather than the field alias. See screenshots below. I believe that if features in a map service have fields with aliases setup, those should be respected in WAB widgets.
I also tried configuring an alias in the popup "configure attributes" settings of the web map. No luck.
So, this idea applies to the filter widget, but there may be other widgets with similar issue. I think it would make sense to respect field aliases in any user interface that end users will encounter, across the platform.