I was having the same problems with it too. I was creating predefined tiles and saving them, but they would not load the next time I played the level even though they were in the tiledefs folders. In order to get them to work I had to create the list, save the list, save the game, and then play the game before closing the game so it can be there the next time I opened the editor. Weird stuff.
And nothing wrong with using predefined tiles. I create my own list often for playerworlds that have different graphics. Plus it helps when I can script an editor control NPC. Gets levels work done much faster.
