Here is an example: template_matrix.json (5.1 KB). The pattern is to create a template widget with everything that needs to change defined in its variables property. The clone matrix then overrides the template's variable property depending on the clone's index.
Now this can get really cumbersome, there is actually a better approach that is to build the widget data in a custom module and edit the interface programmatically (example), this way you'll be able to manage you sample lists in a much more efficient way.