I did want to answer earlier, but I was really busy lately. The purpose of the extension point is to add more nodes to the GPD as you might expect. It was kind of possible to do that in the previous designer. With the new one, I am trying to much better all the extension point parameters and this is not yet finalized. Internally, I do not use the extension point as I should yet. But the idea is definitely to go in that direction. You can expect me to work on that after I have released the GA release of the GPD 3.1.0.