UPDATE: in order to save and load your devmode levels you must make a new folder called levels in the super meat boy directory.
Devmode is NOT the "Level Editor", it is a developer tool that was accidentally left in the Pc build of Super Meat Boy that was found by the mod community.
We do not support updates to Devmode, nor do we answer support questions for it. This post is being made purely to allow people to play around with, its buggy, rough and not supported.. but its also the tool i used to make 99% of the levels in the game.. so you can do a shit load of cool stuff with it.
Technically Devmode is a very loose and not at all user friendly version of the upcoming Level Editor, you can do a lot with it, but its messy and learning the basics can be a bit complex.. but here is the basic run down on how to enable it if you want to play around with it.
Go to Library, then Right Click on Super Meat Boy and go to Properties
Click on Set Launch Options
Type in -devmode in the launch options.
Run the game and it will launch in devmode.
NOTE: if you want to go back to playing the normal game just remove -devmode and you'll be back to normal.
There has been a lot devmode use in the modding community lately, Gpro has actually taken a lot of time out of his days to make a very in depth set of video tutorials that will basically fill you in on everything you need to know.
Have fun playing with devmode, its a nice little precursor to the level editor we have in the works, SAVE YOUR LEVELS! all levels made in devmode will be easily loaded into the editor when it comes out in Jan.
ill conclude this with a level made by the Gpro, called the kid returns. please dont make all your levels this fucking hard...