Sort Mix and Match children alphabetically

wc-mnm-alphabetical-sorting.php

<?php

/**
 * Sort the mix and match children alphabetically
 * 
 * @param array $children : an array of $product objects
 * @param obj $product : the container product
 * @return array
 */
function mnm_order_children_args( $children, $product ){  
    uasort( $children, 'mnm_alpha_order_children' );
    return $children;
}
add_filter( 'woocommerce_mnm_get_children', 'mnm_order_children_args', 10, 2 );

/**
 * Callback for uasort
 * string compare the post titles
 *
 */
function mnm_alpha_order_children( $a, $b ){
    return strcmp( $a->get_title( 'edit' ), $b->get_title( 'edit' ) );
}

If the code does not work try to replace the filter with wc_mnm_child_items
Thanks

woocommerce_mnm_get_children is definitely deprecated. So wc_mnm_child_items is the right path. But the array of items is not the same as the array of products used to be so not entirely sure if the rest works.