The structure for your Library should follow a structure that you can understand and use. For example, when I am drawing details I like to have a symbol folder with all my steel sections, another symbol folder with all my timber sections and a symbol folder with all the standard window sections. When I put a detail together it usually consists of typical construction elements, the timber, steel and window for example. Then there a many components that you draw that do not fit a regular shape. The concrete slab is one that will not always be the same.