Inside the editor currently you are able to change the "Type" of an object, however it only has S2's default types, and requires you to manually edit the "entitylist" if you want to add any custom objects to the map.
I didn't like that, so I made this mod for you! Extract resources0.s2z into "/Heroes Of Newerth/editor/"
Insert the type you want to use, press enter and you're done!
I still left the old dropdown box as well, you have the option of both.