Add snippet of first post into forum list
@sofy thanks very much.
I've asked deveolpers and the best way to do it I'll describe below.
You should customize the forum-thread.php file in the wp-content/plugins/wpforo/wpf-themes/classic/layouts/4/ folder.
Add the following code in the file. The code will show the body of the first post. I've attached the image below, please check it. On the screenshot, you'll see the row you should add the code.
$topic = wpforo_topic($topicid);
$first_post_body = wpforo_post($topic['first_postid'], 'body');
As I've mentioned the code will just show the body of the first post. You'll need to add some CSS code, to display as it should be.