We found SAP note 2529654 describing this issue, and it says that the cause of this issues is: “In Partner Development tenants, the creation of KUT fields is not supported”. https://apps.support.sap.com/sap/support/knowledge/en/2529654
Can we solve this issue and could you give us some detailed explanation? Why this operation is not possible in partner development tenant? In which tenant this can be possible?