VERIFIED SOLUTION i
Key field gets displayed on the key field screen of EngageOne Interactive with the property 'Visible on xForm' is OFF at EngageOne Designer level. This is not an expected behavior. It should be displayed only if 'Visible on xForm' is ON.
This is a known defect in earlier releases of EngageOne.
ResolutionUPDATED: September 4, 2018
This has been fixed in EngageOne Server version 4.4.7. Hence, upgrading to EngageOne Server version 4.4.7 or later should resolve this.