<?php
// add new column to the columns array
function wpse267793_columns($columns) {
    // Column name
    $columns[\'template\'] = \'Template file\';
    return $columns;
}

function wpse267793_show_template_columns($name, $post_id) {
    // get template file name from post meta
    $template = get_post_meta($post_id, \'_wp_page_template\', true);
    echo $template;
}

// change \'CPT\' to the relevant custom post type
add_filter(\'manage_CPT_posts_columns\', \'wpse267793_columns\');

add_action(\'manage_CPT_posts_custom_column\',  \'wpse267793_show_template_columns\', 10, 2);

• manage_posts_custom_column
• manage_posts_columns