Place the Viauslization of the data in a DataTemplate and create two HierarchicalDataTemplates where you set the ItemTemplate to the created DataTemplate. There exist no reason why you shouoldnt create two HierarchicalDataTemplates. They offer you exactly the parametrization you wish and allow you to use the same ItemTemplate for both.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.