It will help to have the video play while you read this
In hopes that others will learn and expand upon this trick I have the explaination for the exit to the knot. Obviously the hard part is throwing the knot. (If anyone would like video of the 1D knot throw I can post that too) After you have the knot thrown, you should be on easy street. The exit is simple but hard to see in the video. A good way to learn the exit is with 1D. Throw the knot with the right hand, then use a clockwise wrap around the axle with your left handstick. Now simply slide the string off of the bottom of your right handstick.
When you adapt that to 2D the sequence goes like this:
1. Throw knot
2. Left handed clockwise back-wrap on free diabolo
3. Carry the left hand diabolo over, then under the right hand diabolo
(at this point the left hand diabolo should be free agian and the right hand diabolo should have the slack-knot and a clockwise wrap around it)
4. The final step is to slide the string off the bottom of your right handstick.
This explaination may be really good or really bad, I can't really test it on anyone locally. Which is why I will freely answer any questions about the trick.