When I pause the game the world options tab allowing me to switch from different game modes and difficulties is not there meaning I have to back out and change it. This also means when I make a copy of a survival world but in creative it keeps me in survival so I cannot change my game mode. The only options I have are Resume Game, Achievements, Marketplace and Save & Quit
There is another button for settings, look at cogwheel icon in the left bottom corner.