Phone - iOS - iPhone 5
My friend showed me how to get more hotbar slots by turning off split touch off and then make the d-pad smaller. I tried it and it worked but then when I saved and quited it and closed out of it on the multitasking thing and went back in to my same world I was back to 5 slots.
1. Go into a world.
2. Press the pause button.
3. Go into the options menu.
4. Turn split touch off.
5. Make the d-pad as small as it goes.
6. Go back into the world.
7. You should have 6 slots.
8. Save and quit to title screen.
9. Double-tap home button and quit out of Minecraft Pocket Edition.
10. Go back into the same world.
11. You should have 5 slots again.