Migrate track last imported time
You have to set setTrackLastImported to TRUE.

What I've done is create a new source plugin that extends the source plugin that I was using and set to true the last imported property.

/**
 * Source plugin that extends "url" source plugin and saves the last imported
 * date.
 *
 * @MigrateSource(
 *   id = "url_last_import"
 * )
 */
class UrlLastImport extends Url {

public function __construct(array $configuration, $plugin_id, $plugin_definition, MigrationInterface $migration) {
    $migration-&gt;setTrackLastImported(TRUE);
    parent::__construct($configuration, $plugin_id, $plugin_definition, $migration);
  }
}


I don't know if it's the best solution, but it works.