It's weird.
I think Steam deleted KFEd.exe from /System here.
I always move out all those script folders from common\killingfloor\ because I REALLY don't want to have them there.
Folders that I extremly frequently have to open, I want it tidy and clear. (to enhance workflow)
The folders Engine - GamePlay - GUI2K4 -... XAdmin flood the folder. >_>
Tripwire, could you change that? Like putting all those script folders into
common\killingfloor\ExportedScripts\
Anyway, if your KFEd.exe is missing because you deleted a folder or moved one, go to Steam, right click on Killing Floor SDK -> Properties -> Local Files -> check for integrity
or something like that.
It will re-download all necessary/missing files again.