I suppose that you could temporarily, start a new 3d sketch, convert the entitiy (the 2d sketch line or spline). Then afterwards, you can delete the "on edge" sketch relation to emilinate its ties to the orignal sketch. At that point (if its a spline that you are dealing with) you can add, delete, control points, or manipulate them in any fashio nt hat you wish. If necessry, you can re-order the sketch back to the point in the feature manager where the original 2d sketch was then use it as its replacement. (this may require you to break any parent child relationships that are tied to the original 2d sketch and reattach them to the replacement sketch if you so need to.
