The Unlink Standard Part command detaches the selected standard part from its thinkparts catalog and converts it into a think3 local component.
You can find this command in the context menu that displays when right-clicking on standard part in a think3 model.
The Unlink Standard Part command effectively deletes the attributes that identify it as a thinkparts component, removes the part number and other part data if assigned, resets its Read only property and, if it was created as an X-Reference, converts it into a local component.
The result of unlinking the standard part from the thinkparts catalog it was originally imported, is therefore a simple local component that can be edited at will.