Currently, all geometries per CityObject are parsed and shown in the viewer. According to the CityJSON specifications, "more than one Geometry Object is used to represent several different levels-of-detail (LoDs) for the same object. However, the different Geometry Objects of a given City Object do not have be of different LoDs." Therefore, if a CityObject contains the same feature multiples times in different LoDs, they should probably not all be shown in the viewer. However, the multiple geometries of a CityObject can also be programmed as different features (although this is technically not how it should be used).
Currently, all geometries per CityObject are parsed and shown in the viewer. According to the CityJSON specifications, "more than one Geometry Object is used to represent several different levels-of-detail (LoDs) for the same object. However, the different Geometry Objects of a given City Object do not have be of different LoDs." Therefore, if a CityObject contains the same feature multiples times in different LoDs, they should probably not all be shown in the viewer. However, the multiple geometries of a CityObject can also be programmed as different features (although this is technically not how it should be used).