Model builders use list hierarchies to create structure in lists.
Create list hierarchies if data needs to be categorized at multiple levels. You can create a parent/child hierarchy in one list, or a composite hierarchy that contains multiple lists, each rolling up to a parent list.
For example, the list items New York, Chicago, and Boston in the G3 Location list roll up to United States in the G2 Country list. United States rolls up to Americas in the G1 Region list. G2 Country is the parent of G3 Location, and G1 Region is the parent of G2 Country.
All Regions is the top level item for G1 Region. Top Level represents the highest level in a hierarchy, and summarizes the data in your list.
Use appropriate name conventions for your list hierarchies. For example, add a two or three-character prefix to each level of the hierarchy.
Manage your list hierarchies in General Lists in the model settings bar.
Note: Open your list in Tree View to easily view its hierarchy.