Filter to add variable stock level totals back to admin

wc-vsl.php

add_filter( 'woocommerce_admin_stock_html', 'tmt_show_variation_stock_level', 10, 2 );

function tmt_show_variation_stock_level( $stock_html, $the_product ) {

    if( sizeof( $the_product->get_children() ) ) {

        $stock_html .= ' (' . $the_product->get_total_stock() . ')';

    }

    return $stock_html;

}