Custom filter on all post page (admin backend)

Question

I have a custom post type called sales_listing. On the All Posts page I have it showing a thumbnail column which is inserted into the postmeta table. It only creates this entry into the postmeta table if you add a thumbnail when creating the post otherwise it doesn't create the entry into the db.

What I need to do is have a dropdown filter (already have the filter showing up) that will only show the post that do not have a thumbnail image so they can be edited later on to add one. I have tried everything I can think of to no avail.

Answer 1

Use the restrict_manage_posts action to add other HTML content beside the Category/Date dropdown filters. Try something simple like:

add_action( 'restrict_manage_posts', 'my_posts_restrictions' );
function my_posts_restrictions() {
    echo 'xxxxx';
}

This should give you xxxxx at the end of yoru filters line. Be warned, as this will appear on any Custom Post Types as well. You need to check your current_screen to make sure you are on the Posts list table, and not any others (like Pages for example).