add nodes on spiro automatically to preserve shape

[dkma]

Say you have a spiro with the points 1, 2 and 3 and the path is some curve. You really like how it looks between 2 and 3, but you want to work on the part between 1 and 2.

Now while you change the way it looks between 1 and 2 it will also change between 2 and 3 although you liked it the way it was. So it would be great if Inkscape could add all points necessary here between 2 and 3 automatically to lock this part while you change the part between 1 and 2.