On the subscriptions list screen in wp-admin change the search order button to be search subscriptions in WooCommerce

functions.php

add_filter( 'gettext', function( $translated, $text, $domain ) {

    // Only target WooCommerce strings in admin
    if ( ! is_admin() || $domain !== 'woocommerce' ) {
        return $translated;
    }

    // Check we're on the subscriptions list screen
    $screen = get_current_screen();
    if ( $screen && $screen->id === 'woocommerce_page_wc-orders--shop_subscription' ) {

        if ( $text === 'Search orders' ) {
            return 'Search subscriptions';
        }
    }

    return $translated;

}, 20, 3 );