How can i undo "Remove bluetooth device" from kitkat?
Make sure your both PC and PHONE are close to each other and the both Bluetooth are turned on and visible for all devices on both then go to your phone and search for devices and see if your PC will appear then try to pair then again.
There is no such a thing as 'undo pairing" you just need to pair them again.
Try that it should work usually if not check if there is any problem with your bluetooth on your pc in device manager.