Get content of publish box

add_action( 'post_submitbox_misc_actions', 'show_current_filter' );
add_action( 'post_submitbox_start', 'show_current_filter' );

function show_current_filter()
{
    $post = get_post();

    print '<pre>' .  $post->ID . ' : ' . current_filter() . '</pre>';
}

• https://codex.wordpress.org/Plugin_API/Action_Reference/post_submitbox_misc_actions
• https://developer.wordpress.org/reference/hooks/post_submitbox_start/