I use WordPress Multisite and made a plugin that adds columns with some data. My code is based on this WP Engineer article. The key function in WordPress Multisite is manage_sites_custom_column. And ...
I do have a custom post type with the following setup: $supports = array( 'title' , 'editor' , 'thumbnail' , 'revisions' , 'page-attributes' ); $args = array( 'hierarchical' ...