Update migrations to import new content I'm using migrate upgrade drush command to generate migrations from a live DB of website.
So content is created during my migrations. How can I do an update of these migrations to import new content when re-run migrations ?

Thanks
You could use the track_changes option, ex.

source:
   plugin: d7_node
   node_type: article
   # Allows to import changed as well as new records from the source.
   track_changes: true


https://www.drupal.org/docs/8/api/migrate-api/migrate-source-plugins/overview-of-migrate-source-plugins#track_changes