The Dimension engineering unit has a screw "pot" on board that can be removed and relocated, used as is, or many other methods too numerous to list.
The OKR can be controlled in a variety of ways as well. Again too numerous to list all the methods, but it could include one of numerous microcontrollers, (again) a simple "screw pot", a digital potentiometer, a power monitoring chip, etc.
The KISS method would be a screw pot or a Digital pot. Other methods I'll defer in elaborating on to when you get the basics mastered.