Each chapter or scene can have a structure label. This is a label which you can use to categorize it.
The labels can be shown on the tree. To do this select Settings -> Appearance and choose how to show the labels in Structure/Roles
Here, they are shown above scenes.
The labels can also be shown on the storyboard
Picking a Label
Select the chapter or scene
Click the Structure Label button
Choose the structure label set
Select the structure label to use.
Downloading Structure Label Sets
Select the File menu
Choose the Downloads option
Select the Structure option and pick the sets to download