Untitled

add_action('salesking_customers_custom_columns_header', function(){
    ?>
    <th class="nk-tb-col tb-col-md"><span class="sub-text"><?php esc_html_e('Commercial registration no','salesking'); ?></span></th>
    <?php
});

add_action('salesking_customers_custom_columns_content', function($customerobj){
    ?>
    <td class="nk-tb-col tb-col-md">
            <span class="tb-amount"><?php echo get_user_meta($customerobj->id,'commercial_customer_number', true); ?></span>
        </div>
    </td>
    <?php
}, 10, 1);