When a 3D group is added, a virtual function AddEdit3DGroup is called, so we need to know what trackerunit we want to add the group to.
Since the addition of a 3D group depends on the type of tracker device, we need to sort this out first. So in CChildFrameConfiguration::OnConfigAdd3DGroup we show a list of all tracker units and we need to pick one:
Once we have a pointer to the tracker device we can call AddEdit3DGroup and pass the tracker unit we want the group added to