Hello Cristian,
Sorry for late response. I think I found the reason: In my company it seems that it is not possible to use Case as related to object.
Here is possible parameters for RelatedTo field:
{
"layoutItems": [
{
"editableForNew": true,
"editableForUpdate": false,
"label": "Related To",
"layoutComponents": [
{
"details": {
"aggregatable": false,
"aiPredictionField": false,
"autoNumber": false,
"byteLength": 18,
"calculated": false,
"calculatedFormula": null,
"cascadeDelete": false,
"caseSensitive": false,
"compoundFieldName": null,
"controllerName": null,
"createable": true,
"custom": false,
"defaultValue": null,
"defaultValueFormula": null,
"defaultedOnCreate": false,
"dependentPicklist": false,
"deprecatedAndHidden": false,
"digits": 0,
"displayLocationInDecimal": false,
"encrypted": false,
"externalId": false,
"extraTypeInfo": null,
"filterable": false,
"filteredLookupInfo": null,
"formulaTreatNullNumberAsZero": false,
"groupable": true,
"highScaleNumber": false,
"htmlFormatted": false,
"idLookup": false,
"inlineHelpText": null,
"label": "Related To ID",
"length": 18,
"mask": null,
"maskType": null,
"name": "RelatedToId",
"nameField": false,
"namePointing": true,
"nillable": true,
"permissionable": false,
"picklistValues": [],
"polymorphicForeignKey": true,
"precision": 0,
"queryByDistance": false,
"referenceTargetField": null,
"referenceTo": [
"API_Request__c",
"Account",
"Account_Scheme_Program__c",
"Acquiring_Contract__c",
"Amendment__c",
"Archived_Email_Message__c",
"Asset",
"AssetRelationship",
"Bank_Account__c",
"CBK_Action__c",
"Campaign",
"Card_Scheme_Program__c",
"Compliance_and_Fraud_check__c",
"Contact_s_Distribution_Item__c",
"Contract",
"Contract_Amendment__c",
"Corporate_KYC__c",
"Descriptor__c",
"Device_Management__c",
"Fee_Details__c",
"Fraud_Investigation__c",
"Gateway_MID__c",
"Gateway_Terminal__c",
"IP_Detail__c",
"Incident__c",
"Life_Management_Action_Item__c",
"Life_Management__c",
"MCC2__c",
"MID__c",
"MOBA_tasks__c",
"Merchant_MCC__c",
"Merchant_Pricing__c",
"Merchant_Pricing_and_Setup__c",
"Merchant_Requirement__c",
"Merchant_Setup__c",
"Merchant_on_boarding_Action__c",
"Monitoring_Details__c",
"NEILON__Admin_Interface_Node_Configuration__c",
"NEILON__Email_History_To_File__c",
"NEILON__File_Access_Control__c",
"NEILON__File_Download_History__c",
"NEILON__File_Email_History__c",
"NEILON__File_Version__c",
"NEILON__File__c",
"NEILON__Folder__c",
"NEILON__Metrics__c",
"NEILON__Tree_Configuration__c",
"NEILON__Tree_Node_Configuration__c",
"Operational_Setup__c",
"Operations_Action__c",
"Opportunity",
"Opportunity_products__c",
"Opportunity_scheme__c",
"Partner_Contract_Amendment__c",
"Partner_Fee__c",
"Partner_Process__c",
"Partner_Product__c",
"Partner__c",
"Person_KYC__c",
"Product2",
"Quote",
"Risk_Assessment__c",
"SFDC_Issue__c",
"SFDC_Project_Team__c",
"SFDC_Project__c",
"Setup_Order__c",
"Setup_and_Integration__c",
"Solution",
"Statement__c",
"System_Access__c",
"Terminal_Merchant_Requirement__c",
"Terminal_Relationship__c",
"Terminal__c",
"URL__c",
"Underwriting_Committee_Issue__c",
"dsfs__CustomParameterMap__c",
"dsfs__DocuSign_Recipient_Status__c",
"dsfs__DocuSign_Status__c",
"dsfs__EnvelopeConfiguration__c",
"rh2__PS_Export_Rollups__c",
"rh2__PS_Rollup_Dummy__c"
],
"relationshipName": "RelatedTo",
"relationshipOrder": null,
"restrictedDelete": false,
"restrictedPicklist": false,
"scale": 0,
"searchPrefilterable": false,
"soapType": "tns:ID",
"sortable": false,
"type": "reference",
"unique": false,
"updateable": false,
"writeRequiresMasterRead": false
},
"displayLines": 1,
"tabOrder": 7,
"type": "Field",
"value": "RelatedToId"
}
],
"placeholder": false,
"required": false
},
{
"editableForNew": false,
"editableForUpdate": false,
"label": "",
"layoutComponents": [],
"placeholder": true,
"required": false
}
],
"numItems": 2
},