Hi wim, there is some information on the node editor here:
https://moi3d.com/wiki/nodeeditor

which will work but it's out of date since it's better to install it in appdata since MoI v4 instead of in "Program files".

Some install instructions on putting it in appdata are here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=11061.15

The advantage to putting it in appdata is you won't have to reinstall it again for every new version of MoI.

- Michael