Ticket #3679: 3679.patch

wordpress.org/public_html/wp-content/plugins/handbook/handbook.php

@@ -241 +241 @@
                         ),
                         'delete_with_user'  => false,
                         'supports'          => array( 'title', 'editor', 'author', 'thumbnail', 'page-attributes', 'custom-fields', 'revisions', 'wpcom-markdown' ),
+                        'show_in_rest'      => true,   
                 );
                 // Allow customization of the default post type configuration via filter.
                 $config = apply_filters( 'handbook_post_type_defaults', $default_config, $slug );