To set the default symbol for a component class definition

In the Project Setup tree view, expand P&ID Class Definitions.
Continue to expand the list until you locate and click the component whose default symbol you want to set.
On the Class Settings pane, in the Property Name column, locate GraphicalStyleName.
In the Default Value column, in the drop-down list, click the symbol you want to use as the default symbol when inserting the component into a P&ID drawing.