I was reading through the URL Parameters Guide and I see that to do something with the Search Widget you need to know the widget_id of the Search Widget, to do something with the Map Widget you need to know the widget_id of the Map Widget, and to do something with a datasource you need to know the datasource_id. These instructions are impossible to follow for the ordinary user as they are never shown anywhere in the Builder UI.
The widget_id needs to be visible somewhere in the Settings Panel for at least the Map and Search Widgets. Why not every widget while you are at it? It would make me happy as a developer. I personally add it to every custom widget I build whether I expect to need it or not. The datasource_id should be on the Data Panel of the UI.
