I can do this through the addFeatureCollection method, but when I create new groups, the feature layers in the groups don't pull in their styles and symbology. Another issue is that when I take my original feature layers and then group them into feature collections, the layer list widget shows both the grouped feature collections, and the original feature layers. Here's what my app is looking like with the code as is.
And here's a grouped feature collection layer that isn't pulling in it's styles:
Does anyone know how I can get the styles for my feature layers and have the layer list widget not display the individual, ungrouped feature layers, but only the feature collections?