About Symbol Parameters
You can include two types of parameters in a symbol:
Node parameters identifying nodes (if nodes are present in the symbol).
Symbol definition parameters, or the top parameter set, identifying the symbol. The system replaces them with the corresponding information when you add the symbol to the drawing. Fixed text appears the same for any instance of the symbol. You can use the following parameters in a symbol definition:
Any of the system parameters for drawings
Any user-defined parameters
&dwg_name
&model_name
&scale
* 
You cannot use a note parameter for the value of variable text.
Depending on the application, a symbol includes the following categories of parameters:
Required
Optional, system-defined
Optional, user-defined
If an application uses a symbol with required parameters, but they are missing, the system issues an error message and you can edit the symbol parameter file.
Creo Parametric uses symbols containing an individual parameter set to create electrical diagrams. You can define Diagram symbols in Drawing mode and Diagram mode. However, if you want to use them in Diagram, you must define them as components or connectors by providing the parameter set appropriate for the type of object the symbol represents (component or connector).