Obviously some function names could do with changing be here you can remove unwanted columns, add new ones and populate the new ones. You can also style the new columns.
add_action('admin_head', 'header');
add_filter('manage_posts_columns', 'remove_unwanted_columns');
add_filter('manage_posts_columns', 'posts_columns', 5);
add_action('manage_posts_custom_column', 'posts_custom_columns', 5, 2);
// Add CSS for new column
function header(){
?>
<style type="text/css">
table.widefat th.column-riv_post_ids,{
width: 50px;
}
</style>
<?php
}
// Remove any unwanted columns
function remove_unwanted_columns($defaults){
unset($defaults['comments']);
return $defaults;
}
// Create a new column called 'ID'
function posts_columns($defaults){
$defaults['riv_post_ids'] = __('ID');
return $defaults;
}
// Populate the new column with the Post ID
function posts_custom_columns($column_name, $id){
if($column_name === 'riv_post_ids'){
echo (int)$id;
}
}