I configured a Journey in marketing cloud with a salesforce event data related to the task object. Everytime a task is created, the lead will entry in the journey. However I need to inject the contact with a different contact key, that is not the Salesforce Lead Id, but it must be an External ID. Have you ever handled this requirement?
In the contact builder -> Data Designer, I tried to change the link between Customer Data and Task (Entry event Data Extension) changing the link from Contact Key <-> Task:WhoId to Contact Key <-> Task:External_Id__c , but any lead is injected into the journey. Do you have any suggestion?