To limit objects that could be parents for Service appointment I should create validation rule that check first 3 characters. Example for work orders: LEFT(ParentRecordId, 3) = '0WO' But: first of all I cant even choose ParentRecord(Id) from the list of fields when creating validation rule. Secondly after typing it manually i recieve syntax error.
Is there any other way to limit parent records (maybe also in user interface -> so user wont have an option to choose for example Account)? Is there possibility to fix above issue?