None of those give you the Current logged in user.
Before you could add code to the file plugins/contact-form-7/modules/special-mail-tags.php I added this code:
add_filter( 'wpcf7_special_mail_tags', 'wpcf7_special_mail_tag_userdata', 10, 2 );
function wpcf7_special_mail_tag_userdata( $output, $name ) {
// For backwards compat.
$name = preg_replace( '/^wpcf7\./', '_', $name );
global $current_user;
if ( 'user_login' == $name )
$output = $current_user->user_login;
return $output;
}
But on 3.9 that file does not exist or at lease i can’t find it.
We need to know how or where to add this code now.