All designs contain a default list of object types and system parameters that can be assigned to each object type. You can add additional object types and parameters, but you cannot remove the default global object types or system parameters. Design objects can have a user-defined set of parameters. Before you can assign a parameter to an object, the global definition of the parameter must exist in the design.

As of Creo Schematics 3.0 you cannot modify system parameters or add values. When you open and verify a legacy design, user-defined values are removed from system parameter definitions. Instanced objects are not affected. The parameter becomes constrained to the list of default values only after the invalid value is removed from the design.