How do activate Debug mode in latest experimental version?

I’m trying to bind the debug button (for when I just want to play around in the game) but I can’t find the keymap file, and the keybindings file is practically unreadable outside of Word, and even then I have no idea what to do. Could someone please help me?

It’s now in the options in-game.

And if you ever want to read code, try Notepad++.