Tested on an iPad Pro 10.5" with iOS v. 11.0.1 and using a SteelSeries Nimbus MFI controller. On the main menu, pressing the "B" button, on the MFI controller, will bring up a popup selection menu with the following text: "Do you want to exit Minecraft?". Selecting "OK" on either the touchscreen or with the "A" button, on the MFI controller, does not exit the game and returns you to the main menu.