I noticed that when I create New Accounts, Only Inbox shows. I assume that I have a Mistake in Config (main.inc.php) file. Any ideas as to what the issue could be? :--)
No issues there. Roundcube does not create folders by default. To have it create Default folder by default, edit main.inc.php:
// automatically create the above listed default folders on first login
$rcmail_config['create_default_folders'] = false true;