Customize the pagination settings for your bbPress forums using the following PHP code snippet. This will allow you to control how topics and replies are displayed across multiple pages:

<?php
function custom_bbpress_pagination( $args ) {
    $args['posts_per_page'] = 20; // Change the number of posts per page
    return $args;
}
add_filter( 'bbp_forum_pagination_args', 'custom_bbpress_pagination' );
?>

With this code, you can set a custom number of topics to be displayed per page in your forum. Simply adjust the value in 'posts_per_page' to suit your needs.