Using drush migrate-import --update I created a migrate script to import hundreds of records into a specific content type. A year after, I need to add another field to the content type and import values specific to each record. Because of changes made to some of the records over the past year, I cannot re-import the content from the csv file with the additional column. I am using config-edit to edit the migrate .yml file. Is there a way to rerun the migration to import content for the new field while ignoring all other fields that already have content.

I am using Drupal 8.

Thanks,
I was able to make it work by doing a vigorous edit of the original migrate script, removing all the fields and their mappings, except for the key. Adding the new field, allowed me to rerun the migrate script and the new field was imported while leaving the other content intact. I am still able to use the rollback and other functions of the script.