Models are presented in list view by default. An alternate view mode is tree view, in which model development is shown as a hierarchical tree.
To switch views, click 
in the toolbar. The icon will change to 
as an indication that you are in tree view mode.
The tree is built using parent/reference information included in the model files (see “Run records”). When creating models in Pirana, this information is added automatically and adheres to PsN’s run record syntax.