Anyone know how to set up new ItemGroups in the stats editor?

I have most of the basics down, and am able to create items and skills, change the crafting list, and whatnot, but I can't get specific items to be able to be crafted in the game. The editor seems to generate the item's model and icon from the ItemGroup. So, for instance, I was trying to set up a way to craft one of those broken swords into the two-hander that had the same hilt, but I can only get it to craft a claymore (WPN_Knight_Sword_2h_human).

There are generally a lot of templates available, but I don't know where to edit the templates, especially since many don't seem to appear in the Root Templates.