You can configure dependent fields to introduce hierarchy in your field choices and organize them into categories and subcategories. Dependent fields allow you to nest each item into various levels of categories.
To configure dependent fields:
Go to Service Management > Service Desk Settings > Field Manager > Ticket Fields > Ticket form.
Select the dependent field type from the Drag & Drop Field options.
The Properties section opens on the right pane.
Select the required behavior properties.
Enter the nested field label names for three levels of hierarchy (for example, Category > Sub category > Item).
Then, enter values for each hierarchy level in the Dropdown Choices box. Ensure to use the tab key to indent values (one tab makes it a level 2 hierarchy, while two tabs makes it a level 3 hierarchy).
Click Preview to preview the configurations.
Click Done. Then, click Save on the Ticket Fields page.