Introduce 'template_name' label to custom post types and custom taxonomies

src/wp-includes/class-wp-post-type.php

@@ -1010,6 +1010,7 @@ public static function get_default_labels() {
 				_x( 'A link to a post.', 'navigation link block description' ),
 				_x( 'A link to a page.', 'navigation link block description' ),
 			),
+			'template_name'            => array( __( 'Single item: Post' ), __( 'Single item: Page' ) ),
 		);
 
 		return self::$default_labels;

src/wp-includes/class-wp-taxonomy.php

@@ -645,6 +645,7 @@ public static function get_default_labels() {
 				_x( 'A link to a tag.', 'navigation link block description' ),
 				_x( 'A link to a category.', 'navigation link block description' ),
 			),
+			'template_name'              => array( _x( 'Tag', 'taxonomy singular name' ), _x( 'Category', 'taxonomy singular name' ) ),
 		);
 
 		return self::$default_labels;

src/wp-includes/post.php

@@ -2083,6 +2083,7 @@ function _post_type_meta_capabilities( $capabilities = null ) {
  * @since 6.3.0 Added the `item_trashed` label.
  * @since 6.4.0 Changed default values for the `add_new` label to include the type of content.
  *              This matches `add_new_item` and provides more context for better accessibility.
+ * @since 6.6.0 Added the `template_name` label.
  *
  * @access private
  *
@@ -2167,6 +2168,11 @@ function _get_custom_object_labels( $data_object, $nohier_vs_hier_defaults ) {
 		$data_object->labels['archives'] = $data_object->labels['all_items'];
 	}
 
+	if ( ! isset( $data_object->labels['template_name'] ) && isset( $data_object->labels['singular_name'] ) ) {
+		/* translators: %s: Post type name. */
+		$data_object->labels['template_name'] = sprintf( __( 'Single item: %s' ), $data_object->labels['singular_name'] );
+	}
+
 	$defaults = array();
 	foreach ( $nohier_vs_hier_defaults as $key => $value ) {
 		$defaults[ $key ] = $data_object->hierarchical ? $value[1] : $value[0];

src/wp-includes/taxonomy.php

@@ -645,6 +645,7 @@ function unregister_taxonomy( $taxonomy ) {
  * @since 5.8.0 Added the `item_link` and `item_link_description` labels.
  * @since 5.9.0 Added the `name_field_description`, `slug_field_description`,
  *              `parent_field_description`, and `desc_field_description` labels.
+ * @since 6.6.0 Added the `template_name` label.
  *
  * @param WP_Taxonomy $tax Taxonomy object.
  * @return object {