I've created a custom editor to include the ability for freehand polygon creation. The widget leverages SktechViewModel and FeatureForm. I was unable to get DataSources to work properly so snapping to specific features can be enabled within the widget code itself. Editable layers should be set from the map but can also be specified in the script.
Hope it helps someone else too.
https://github.com/adrienhoff/Experience_Builder_Custom_Widgets/tree/main/Sketch
