The current Coordinate Widget in the Web AppBuilder uses static JSONs to set up the coordinates and transformations before making a call to the Portal registered GeometryServer to carry out the transformations etc. The coordinates only work dynamically when the WebMap is using GCS_WGS_1984 or Web Mercator. Since JavaScript version 4.7 (and 3.24) there has been the ability to use client-side projection and transformation (less for GRID based transformations). It makes sense that the Coordinate Widget should use the latest capability in JavaScript rather than rely on the static JSON and Client-Server current implementation.
This would mean that coordinates, including tranformations, could perhaps be shown dynamically and not be reliant on the user clicking the screen to initiate the call to the GeometryServer. This would give a better user experience and enhanced capability.