The source code of Operations Dashboard is not open and the built-in functions are not extensible, so a custom widget will be the way to go. However, there is a Dashboard sample implementing a list widget with feature actions that comes with the WPF SDK. The location of the sample's source code is typically at: C:\Program Files (x86)\ArcGIS SDKs\WPF10.2.3\sdk\samples\sampleapplication\Operations Dashboard Samples\WidgetWithFeatureActionsCS. You can take it as a reference when you develop your custom list widget.
Thanks and any questions please let me know,