Modify the file “form-topic.php” (located in “/wp-content/plugins/bbpress/templates/default/bbpress/form-topic.php”):
32 <form id="new-post" name="new-post" method="post"
action="<?php the_permalink(); ?>">
Change it to:
32 <form id="new-post" name="new-post" method="post"
action="<?php echo the_permalink() . "?redirect_to=/question-awaiting-moderation/"; ?>">
Upload this modified file to: “/wp-content/themes/YOUR_THEME/bbpress/form-topic.php”
Do the same for the replies if you are moderating those (form-reply.php).