Just putting this here for people searching in the future.
Since UnRen isn't always an option (linux/mac), here's the relevant bit of what it does:
Create a new text file (.rpy extension) in the renpy/common subdirectory and name it whatever you want, as long as you aren't overwriting anything. I named mine 'enable-dev.rpy'.
The entire contents of the file are:
Python:
init 999 python:
config.console = True
config.developer = True
Save and you're done. Shift-D for debug mode, Shift-O for the console.
Attached is a copy of mine, for the lazy.