Jack-O_Freak: I actually having the same problem
You should just need to hit FN-F11 if your computer has mapped the function keys to other features by default.
In the Developer Mode version of the game, there is a warning in red text on the left side of the main menu screen about using the Developer Mode and a mention of bring up the cheat window with F11.
If you hit the windows key, does that bring up a start menu in Windows 8? If you can not find the game's shortcuts that way, try hitting Win-E and see if that brings up Windows Explorer, to let you browse to the folder where you installed the game.
If the Search feature is east to get to, you could search for Divinity2-debug.exe (you might need to go into the advanced options to have it search in hidden and system folders if you installed the game in the Program Files path.