Resource Context sensitive help

On the Adido website there is a page describing why MODX is so great. About half way through there description they have an image of a resource tree and a pop-up menu that seems to be customised: in this case for Rings along with a custom icon. Does any body have any ideas on how this is done?

http://blog.adi.do/2013/08/modx-v-wordpress-its-apples-and-oranges/

Looks like a Custom Resource Class, something like Articles. http://rtfm.modx.com/revolution/2.x/developing-in-modx/advanced-development/custom-resource-classes

At this point the new docs aren't all working correctly; you can try the same thing at the old doc site http://oldrtfm.modx.com/display/revolution20/Custom+Resource+Classes