Put featured image under post title in admin area

add_action('admin_head-edit.php', function(){
    add_filter('the_title', function( $title, $id ) {
        return $title . the_post_thumbnail( 'thumbnail' );
    }, 100, 2);
});

Will produce 2 images because there are two titles on custom posts, apparently. One that is hidden and one that isn’t. Adding the image markup to the hidden element will break the CSS that hides it. So the solution is to insert admin-css that hides it.

    .column-title .hidden ~ img{
        display: none;
    }