Hi kryvulena. You can achieve that editing the plugin file custom_upload_dir.php as follows:
ORIGINAL CODE
function cud_generate_path(){
global $post, $post_id, $current_user, $cud_file_ext, $cud_file_type, $cud_rpc_id;
MODIFIED CODE
function cud_generate_path(){
global $post, $post_id, $current_user, $user_id, $cud_file_ext, $cud_file_type, $cud_rpc_id; // variable $user_id added to the code
ORIGINAL CODE
$customdir = str_replace('%current_user%', cud_get_user_name($user_id),$customdir);
MODIFIED CODE
$customdir = str_replace('%current_user%', cud_get_user_name($user_id),$customdir);
$customdir = str_replace('%current_user_id%', $user_id, $customdir); // this line added to the code
ORIGINAL CODE
'current_user' => __('The currently logged in user', 'cud'),
MODIFIED CODE
'current_user' => __('The currently logged in user', 'cud'),
'current_user_id' => __('The currently logged in user ID', 'cud'), // this line added to the code