Edit Default Graph Widget?

Hi,

I'm looking to make a minor change to the graphs that can be added to the Dashboards section. I can see that various widgets have been added here and can be customised, but as far as I can tell the default "Charts" selection isn't present in the Widget library (unless I've overlooked it). Is there a way to reach this, or to duplicate the code into a standard widget in the library that I can then go into the files and make changes to it?

The widget description: