New structure levels will be added to the Structures tab. Structure levels are assembly levels under which there can be either lower assemblies or single parts. Structure work phases can be related with assemblies like welding or with handling a completed part assembly like painting or delivery.
If you change the ordered count of a structure level or the count of parts, that change in the count is also updated for the lower levels.
If you delete a structure level, the parts beneath it are also deleted.