How to sort category by custom field value

Your question it make sense to me my friend but the get_categories don’t have the option to order by “meta_value_num” and then order by custom fields.

What you can do is order after you get the array using the usort php function:

    $all_subcategories = array('parent' => $categoryID);

    $categories = get_categories( $all_subcategories );

    function order_categories($a, $b) {
    if ($a->term_id == $b->term_id) {
        return 0;
    }
        return ($a->term_id < $b->term_id) ? -1 : 1;
    }

    usort($categories, "order_categories");

It work fine for me. I used ACF to add the category order field but is fine the way you made it and should work.