How do you make the small keyboard go back to the large one, pinching doesn’t work. Dragging it to the bottom doesn’t either.

To easily return the new Floating Keyboard to the normal on-screen keyboard presentation, use the two-finger “zoom” gesture (i.e., the reverse of the two-finger “pinch”).

If the Split Keyboard is restored instead of the full on-screen keyboard, you can either use two fingers (one on each of the two half-keyboards) and swipe the two halves together - or touch-and-hold the “keyboard” key, then slide your finger to the Merge & Dock option and release.

Use the floating keyboard on your iPad – Apple Support

Split and move the keyboard on your iPad – Apple Support

Just use two fingers - simultaneously placed on the small keyboard - and separate your fingers…