Currently it’s not possible to use on import the “DON’T OVERWRITE EXISITNG VALUE” function. At the moment this is only working in combination with email.
It would be great to get the same function for the import in combination with CONTACT ID. This will help to easier update blank records with data from a list without the need to analyze, manipulate/scrubbing and reducing.
So, only blank records will be filled with relevant data from the import.