Cool, I've been trying to get to that developer menu too and it's annoying me, because I just cannot find it.
Which methods of finding it have you tried so far?
My main method has been trying a few common
Command Line Arguments, but I've had no success so far.
I've also been looking in other files, looking for ways to access this mode.
Particularly
levels.txt has my interest as it has a developmental mode type feature which works but so far hasn't gotten me that menu I have been looking for.
Thist url I have provided above links to a technique you can use to do what developers want to do, there isn't all that much you can do with this feature that you could do with the Developer Mode but it's still a lot of fun!