removing saved icons

Anyone know how I could remove some of the saved icons in the icon rules area? Until I actually see them in Calibre I don't know if I want them, but by then they are stuck in the list.

I hunted around for the images file but I can't find the one associated with this aspect of Calibre (icon rules).

I checked the app data roming for images, the book cover images and a couple of other ones are there, but that's only a couple. I need to remove dozens.

(duh..cc_icons)