Pilou,

You could use curves/rectangle followed by construct2/planar, or
alternatively add these nodes to nodes/extension folder:
http://moi3d.com/forum/index.php?webtag=MOI&msg=7777.1710

I want to overhaul the node libraries but it will be a major project
for which I don't have time for in foreseeable future.

James
https://www.instagram.com/nodeology/