By drag and drop on the elements in the list you can change the order or hierarchical structure of the geometries. The order of the geometries is important if they have transparent materials. Transparent objects must be as low as possible in the list and thus will be arranged in front of the other geometries.
The hierarchical structure of the geometries allows the subordinate geometries to take over the transformations of the parent geometries. In this way the objects in the scene can be animated and groups of geometries can be transformed. Grouping geometries also helps to clone or export a certain structure of geometries.
* Try drag and drop geometries list items