Spare parts can be sold both assembled and in component parts. For example, you can add a part "Door assembly", and then clarify its composition and add "Door impact sensor", "Door lock", "Frame", "Cladding", etc. In order to add nested spare parts to the door:

Add a basic spare part, for example, "Engine assembly".
After the spare part is selected, next to the field, expand the list with collapsible spare parts.
Specify collapsible spare parts and when creating the main spare part, collapsible parts will be created by separate spare parts with photos of the main one. If there is no collapsible spare part, contact technical support to add it.