As in the screen where you select what you want to use.
This is on the M8, you have a bit less icons on the M7 since it got less camera modes.
It’s pretty straight-forward. Select what you want to move and long press it, and move it when it “unlocks” from the order it’s in.
And just simply drag it to the place where you want it, and simply repeat until you have it in the order you want.