You can use an extended hierarchy if a hierarchy node is to be assigned to several parent nodes. However, the node that is assigned multiple times must always be assigned at the same hierarchy level.

An extended hierarchy can make sense in processes of transportation planning/vehicle scheduling (TP/VS), for example, in which a plant delivers materials to a customer and several alternative itineraries involving different transshipment locations (such as ports) are available. In this case, you can use an extended hierarchy to assign a plant (hierarchy level 2) to several transshipment locations (hierarchy level 1), for example.