Natural Entity Spawn Condition

Hi,

anyone there with good experience to help me ?

I am trying to use on an entity "Natural Entity Spawn Condition" procedure but nothing happens. Is it bugged ?

I create my entity, I go in the spawning section and there I click + to add a new procedure. I create the new procedure but then I can't add it to the box.In the box only choice remaining is the standard one "use vanilla condition"

Pleas help