[prokops]

Here is a functions / snippet code version for anyone else looking:
—

function my_forums_dropdown_shortcode() {
    // Start buffering output
    ob_start();

    // Dropdown container
    echo '<select id="forums-dropdown" onchange="location = this.value;">';
    
    // Forum loop
    if ( bbp_has_forums() ) :
        while ( bbp_forums() ) : bbp_the_forum();
            $forum_permalink = bbp_get_forum_permalink();
            $forum_title = bbp_get_forum_title();
            echo "<option value='{$forum_permalink}'>{$forum_title}</option>";
        endwhile;
    else :
        // No forums found
        bbp_get_template_part( 'feedback', 'no-forums' );
    endif;

    // Close the dropdown
    echo '</select>';

    // Return the buffer contents
    return ob_get_clean();
}
add_shortcode('forums_dropdown', 'my_forums_dropdown_shortcode');

Just paste in [forums_dropdown] where you want output.

[prokops]

It would do the trick but it is not the best solution :/
I will try to develop an submission verification based on user custom field.

[prokops]

I can delete the email field in the file you specify. But the forum still tries to validate and thus gives me an “ERROR: Invalid email address.”

How to define what to validate and disable email field validation?

Cheers