Hello Michael,
I was on the wrong path:

\Users\self\Library\Application Support\Moi\commands\Rectangles.htm.

Now I have changed to

\Applications\MOI V4\MoI v4.app\Contents\Resources\commands\Rectangles.htm

made the changes and - it works!

Sorry if I stole your time.

But when updating to a new version I have to do the inputs again?
-moritz