you can also add them by opening up the .ved file in a text editor like notepad++, sublime text etc & manually type in the new interfaces... make sure you create a backup of your .ved first though.
I wrote a mini guide on adding them ages ago... it seems that I hosted the image files on my old website though - doubt I still have them anywhere, but here was the thread: http://www.visionaire-studio.net/forum/thread/want-more-inte...
-- * --
in the explorer tool what happens when you right click on eInterfaces
? for me it brings up the option create 'interface'
& then adds a new interface inside of eInterfaces tree. If it's not working then maybe it's a bug in the current release? I'm on a slightly newer build than what has been shared to the public.