Adding custom fields to listing display

In the ‘Page Setup’ area of the admin, I have the Recent Listings on the home page.
I am wanting to add certain custom fields to the listings but can’t see how to do this without modifying the core?

I can see that the listings are being created with class_white_label_themes.php and the DEFAULT_WIDGETBLOCKS_OUTPUT function so wondering what the best way to override this is?
Would copying the whole (rather large) function to the child theme be the best way?

Cheers