Divide Meta Fields with Comma (Really Simple CSV Importer add-on)

rscsv-divide-meta-fields.php

<?php
/*
Plugin Name: Divide Meta Fields with Comma (Really Simple CSV Importer add-on)
*/

add_filter('really_simple_csv_importer_save_meta', function($meta, $post, $is_update) {
    foreach ($meta as $key => $value) {
        if (strpos($value, ',') !== false) {
            $_value = preg_split("/,+/", $value);
            $meta[$key] = $_value;
        }
    }
    return $meta;
}, 10, 3);