You can modify a derived part. However, you must specifically update the derived part to incorporate changes made to the original part. Derived parts are not updated automatically. You can control when changes occur in the derived component.
Update a part with active links
When a base part is modified, the derived component appears with a red lightning bolt in the browser, indicating that it is out of date.
To update the component, click Update 
on the Quick Access toolbar.
Note: Derived parts with active links are flagged for update only when the objects they reference are modified.