The Selections box from the PropertyManager and the corresponding File Explorer folder and file structure are set up as follows:

• home folder. Contains one or more standard folders. In the example below, weldment profiles is the home folder, and contains two standard folders (ansi inch and iso). In the PropertyManager, the name of each standard folder appears as a selection in Standard.
• standard folders. Contain one or more type folders, for example angle iron, c channel, pipe, and so on. In the PropertyManager, after a Standard is selected, the names of each of its type sub-folders appear in Type.
• type folders. Contain one or more library feature parts. In the PropertyManager, after a Type is selected, the names of the library feature parts appear in Size.

Structural Member PropertyManager and File Explorer:

Source: Solidworks Help