Import simple array into WordPress using Import Users From CSV

import-users-from-csv-array.php

<?php
/**
 * In your CSV file, you may set the array value to {value1,value2,value3}
 * This will import array values into WordPress.
 * To add this code to your site follow this guide - https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/ 
 *
 * Integrates with Import Users From CSV - https://wordpress.org/plugins/import-users-from-csv/
 */

function my_import_user_meta_csv_array( $meta, $userdata ) {

    // Loop through meta to get arrays.
    foreach( $meta as $key => $value ) {    
       $reg = '/( { ( (?: [^{}]* | (?1) )* ) } )/x'; 
       preg_match_all( $reg, $value, $matches );

       if ( ! empty( $matches[0] ) ) {
        $string = substr( $matches[0][0], 1, -1 ); // remove curly braces.
        $array = explode( ',', $string ); // convert to PHP array.

        $meta[$key] = $array; // assign the key to an array.
       }
    }

    return $meta;
}
add_filter( 'pmproiucsv_import_usermeta', 'my_import_user_meta_csv_array', 10, 2 );

This recipe is included in the blog post on "Import user meta fields that are stored as an array (select2/multi-select and checkbox)" at Paid Memberships Pro here: https://www.paidmembershipspro.com/import-user-fields-stored-as-an-array-select2-multi-checkbox/