Many of the more advanced options for the Editor Widget are handled indirectly through the Smart Forms functionality in the Web Map Viewer. Smart Forms can be used to add Arcade expressions, extract data from other layers, set a priority level for different layers, populate features with default values, fetch location attributes, and setting fields to be editable, required or hidden.
See the official ESRI blog post for more information.
Here's an article describing how to override calculated values.
