I am creating a kitchen scene, and in order to create cabinets I am using door objects made in archimesh. The problem is when I try to duplicate the doors, the only way to do this is to select all of the separate objects (or shift-g from the empty that is created). I found this post: How to duplicate the empty which says to use dupligroup, but I cannot find it in blender 2.8.
You could select the empty in the outliner and right click on it and choose select hierarchy. In this example the separate objects are parented to the empty. This is done by dragging the object into the empty in the outliner and holding the shift key.
In the object window (not the outliner) press shift + d and a copy will be made