Hi Lars, Blend can sometimes be used for a hole like this, but right now Blend is limited to only working between 2 edges.

So if you have one big edge, this can be done by using Edit/Trim along with the "Add trim points" option to split the edge into 2 pieces, then you can use Blend between those 2 to make a kind of fill. But this may not behave well in an area of inflection curvature like you have in this case.

There isn't currently a way to merge edges that are already split up into smaller pieces into larger edges yet.

Probably right now your best bet would be to use a rectangle to trim out a bit more area and then do a Network on those rectangle edges (use Join to glue together small pieces into one curve where they cross the seam edge).

That's what I did for the attached hole_patched.zip file.

The result is not perfectly smooth, but it is pretty close. If you could find some way to get an additional proper guide curve running through the middle that would probably help get it closer. Also if you were a bit more careful than I was to make the rectangle a little smaller that would probably help some more too.

Sometimes it is helpful to use Edit/Separate to break your model apart into different pieces so it is easier to work on just one piece at a time for stuff like this, then use Edit/Join later on to glue it back together again.

I do have plans to add a different type of hole-patching mechanism in the future.

Hope this helps you for now though,

- Michael