thank u so much for the deep dive answer i got to my question. 
i just realized, that i tried to make my problem kind of easier, because i expected an easy answer or concept that i could use for my issue. 
maybe its better to share the code i adapted from another blender user  :
[<img src="https://blend-exchange.com/embedImage.png?bid=pOy7OZ8O" />](https://blend-exchange.com/b/pOy7OZ8O/)

every side of the main-mesh-plane has a fix element (in the picture example 6m) and the rest is averaged at the ends (x). This x is changing everytime i change the size of the fix element, or when i change the form of the main mesh-plane.

for architectural purposes, i managed to extrude the main fassade elements but not the corners.
[![enter image description here][1]][1]
[![enter image description here][2]][2]

are the mentioned concepts still useable for this specific issue? 

thank u so much for ure time!


old post:

"First time around here and hope to get some help for this problem:
I didn't manage to fill the corners of this setup with faces. I got only the vertical edges but not the horizontal ones, which I could easily extrude.

Quite new to geometry nodes...

[![my setup so far][3]][3]

Appreciate any idea / suggestion!


  [1]: https://i.sstatic.net/CmD7D.png
  [2]: https://i.sstatic.net/tbkOO.png
  [3]: https://i.sstatic.net/qS6hh.png"