Cookbook: hierarchical categories

Where in the UI. Structure: categoryDef nodes. Connect parentDef → childDef. Properties hang on the owner.

1. Create category “Vehicle” with property “License plate” (text).
2. Create child “Car” with property “Doors” (integer) only — do not copy License plate.
3. categoryRef the child (or the parent) on the element as your product needs.
4. On a layout, bind plate using categoryId of Vehicle, and doors using Car.

Users who assign Car still have a plate field, because ancestors are included at runtime.