Looking at that control panel (thanks for uploading!) and assuming there's a matching panel in the other cab, then the marker lights are set in cab 1 or end 1 and cab 2 for end 2. There is only one switch for each colour. It's presumably possible to have (albeit incorrectly) all the white and red marker lights on on both ends simultaneously. The driver needs to manually check that they have switched the unneeded ones off, as well as switching the needed ones on. It's not a case of "turn on end 1 white lights and end 2 white lights will extinguish". There is no remote control of the marker lights at the other end. The driver needs to walk to the control panel at the other end to set the marker lights at that end. That's what I would assume looking at the control panel pictured. Anyone know any better?
Edit: Was the Baby GM running light engine at the open day?