The run player is part of the nodecg-speedcontrol bundle and has not had any modifications from its public version. The run player controls the active that is displayed on the stream, and acts as a quick point of reference for run details. Because the Live Switch automatically advances runs when switching to intermission, you shouldn't need to perform any actions on this panel, it should just act as a source of information. The only action to take is when you first start the marathon, you'll need to advance to the first run of the event - after that the Live Switch should do the rest. The run player can be useful though for correcting mistakes, such as going back to a run that's been accidentally skipped.