Relation meta key is not shown in JetEngine

Hi there

I made two custom posts by JetEngine one is for Destinations and other for Tours, then i set Relation between the two custom posts. and i set it to One-Many (As each single Destination can have many tours.

When i Click Add relation, and it back to the Relation tab, ididn't find any tap called "Relation meta key" and there is no tutorial talking about this!