And don't forget the swipe functions....once the keyboard is up, you can simply use that same key to drag it up...and it will split automatically. Once it is split, you can use two fingers, one on each size, at the same time, and pinch them together. The keyboard will unsplit...and remained undocked. Two fingers again (one swiping to the right, the other to the left) will split. I find this faster than using the press and hold option, if you have two fingers free.
I wish my android tablets has this split/undock feature.