Add selected grouped layer from webmap

What I would like to provide is a workflow in which a user can select one or more grouped layers (Operational layers) and add those (including sublayers) to the Viewer. I have set up a display form in wich the grouped layers can be selected. The next step is to add the selected layers to the Viewer.. And that is what I am not able to do. Does anybody has a solution for this.

What needs to be used as parameter in the Run Command activity and how to get it there?