In order to preserve the integrity of the standard part content library, AutoCAD Mechanical toolset does not let you modify geometry or constraints.
You can only change information in the Family Table. You can:
This translates to adding a part to an existing family of parts. For example, a screw identical to one in the standard parts database, but with a different length.
Typically you change the value of a cell to change the material of a specific item in the library, or modify a property such as the density.
We make a special mention of changing the values in the PAST column. This column controls what preselection filter the selected row reacts to. Preselection filters group standard parts as Standard and Company parts. In AMOPTIONS, in the AM:Content tab, you can set a preselection filter, which tells the system what group of standard parts to display. Hence selecting parts for insertion in a drawing becomes easier as you only see a filtered list.
This translates to adding a column such as vendor or recommended price, which in turn appears in the BOM.
If you want to modify the geometry or constraints, in the Content Manager, drag the item to a custom content library. Once the item is in a custom content library, you have unrestricted access to all available customization tools.