Take longitudinal curves / Rebuild as you want
Hide Point
Then LineWeb / Curve (order of selection curve is important! )
Trim
Network / Lighter if you want a surface (Move Points before ask Network ! )
Et voilĂ ! :)
Hi Matadem, the "Add pt" command in MOI will also raise the degree of the surface to degree 3 if it's lower than that, like if it is a plane with just 4 corner points.