This is hilarious. It does work.

WTF, Bethesda? (not my find, btw)...

http://www.nexusmods.com/fallout4/mods/1330/?

They must've hid it like that for debugging.

This may be something with the newest patches. I'm still running the original executable in borderless window mode and it doesn't work.

This is probably what did it.

[Launcher]
bEnableFileSelection=1

Very likely. They'll probably add the "Data Files" option to the launcher when the CK releases.

Or they have that as a placeholder, and add it properly to the launcher once they have launched the mod tools.

Yep, that did it. You have to add the line to your My Games\Fallout4\Fallout4Prefs.ini file.