I'm being part of the beta of the level editor, and the truth is that it has a great potential to expand the possibilities of the game, however, in the time I've been using it I would like to give the following recommendations:

1) Improve performance: My PC consumes a lot of CPU when I have the level editor open, and also when I test the levels. The performance sometimes drops, not a lot, but it's a bit annoying. Also I want to add that the game in my pc has some instability, I know it is a beta, but they could be correcting the performance with the passing of the days.

2) Add hordes mode in the editor: Horde mode only has 3 fabulous maps in the game, it would be great to make more hordes levels to take advantage of many concepts, like a hordes map in the cemetery, or to recreate hordes maps from other games, such as call of duty, serious sam, etc. So far you can only create custom levels, but hordes mode could be leveraged quite well too.