DreamedArtist: NO KIDDING! Now I am re installing the game right now and trying to figure this shit out on how to unlock it. I finished the game once 100% it and doing a new game plus and mid way in...
GR00T: Had to look it up: it's part of the Blood and Wine expansion. I won't go into spoilers, but there's a quest chain that will lead you to unlocking that menu.
That is something I've read before... where was that ... ah yes, I posted it just a few minutes ago ;)
" other the mutation menu which was added with blood and wine."
Well... so we can all agree that GOTY is not that different from base + expansion ... just another urban legend (however there is one tiny difference: in GOTY the menu is changing randomly).