As requested, I have added an option to test the World Editor without logging in. You can sign up from inside the World Editor itself to publish, or you can download the world's file to your computer and re-upload it later to continue building.
I've also made a number of other UX tweaks which should hopefully make things clearer for new players.
Anyone want to give it another go? At the very least, I'm hoping it should be clear enough to build something using the Legendary Dungeons package.