Demonstration

Custom ID field

Solution

Insert the code bellow in your theme’s function.php file.

function postsColumnsHeader($columns) {
	$columns['postID'] = __('ID');
	return $columns;
}

add_filter( 'manage_posts_columns', 'postsColumnsHeader' );

function postsColumnsRow($columnTitle, $postID){
	if($columnTitle == 'postID'){
		echo $postID;
	}
}

add_filter( 'manage_posts_custom_column', 'postsColumnsRow', 10, 2 );

You might also want to check out how to do this for pages listing and how to do it for categories listing.

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