diff --git a/src/wp-admin/menu.php b/src/wp-admin/menu.php
index 71fd94b2e3842..a756fa40f3624 100644
--- a/src/wp-admin/menu.php
+++ b/src/wp-admin/menu.php
@@ -205,10 +205,12 @@
 
 if ( wp_is_block_theme() ) {
 	$submenu['themes.php'][6] = array( _x( 'Editor', 'site editor menu item' ), 'edit_theme_options', 'site-editor.php' );
+} else {
+	$submenu['themes.php'][6] = array( __( 'Patterns', 'site editor menu item' ), 'edit_theme_options', 'edit.php?post_type=wp_block' );
 }
 
 if ( ! wp_is_block_theme() && current_theme_supports( 'block-template-parts' ) ) {
-	$submenu['themes.php'][6] = array(
+	$submenu['themes.php'][7] = array(
 		__( 'Template Parts' ),
 		'edit_theme_options',
 		'site-editor.php?path=/wp_template_part/all',
@@ -220,7 +222,7 @@
 // Hide Customize link on block themes unless a plugin or theme
 // is using 'customize_register' to add a setting.
 if ( ! wp_is_block_theme() || has_action( 'customize_register' ) ) {
-	$position = ( wp_is_block_theme() || current_theme_supports( 'block-template-parts' ) ) ? 7 : 6;
+	$position = ! wp_is_block_theme() && current_theme_supports( 'block-template-parts' ) ? 8 : 7;
 
 	$submenu['themes.php'][ $position ] = array( __( 'Customize' ), 'customize', esc_url( $customize_url ), '', 'hide-if-no-customize' );
 }
diff --git a/src/wp-admin/site-editor.php b/src/wp-admin/site-editor.php
index 6442ee562b0a1..70d646ae51f36 100644
--- a/src/wp-admin/site-editor.php
+++ b/src/wp-admin/site-editor.php
@@ -19,16 +19,19 @@
 	);
 }
 
-if ( ! ( current_theme_supports( 'block-template-parts' ) || wp_is_block_theme() ) ) {
-	wp_die( __( 'The theme you are currently using is not compatible with the Site Editor.' ) );
-}
-
 $is_template_part        = isset( $_GET['postType'] ) && 'wp_template_part' === sanitize_key( $_GET['postType'] );
 $is_template_part_path   = isset( $_GET['path'] ) && 'wp_template_partall' === sanitize_key( $_GET['path'] );
 $is_template_part_editor = $is_template_part || $is_template_part_path;
-
-if ( ! wp_is_block_theme() && ! $is_template_part_editor ) {
-	wp_die( __( 'The theme you are currently using is not compatible with the Site Editor.' ) );
+$is_patterns             = isset( $_GET['postType'] ) && 'wp_block' === sanitize_key( $_GET['postType'] );
+$is_patterns_path        = isset( $_GET['path'] ) && 'patterns' === sanitize_key( $_GET['path'] );
+$is_patterns_editor      = $is_patterns || $is_patterns_path;
+
+if ( ! wp_is_block_theme() ) {
+	if ( ! current_theme_supports( 'block-template-parts' ) && $is_template_part_editor ) {
+		wp_die( __( 'The theme you are currently using is not compatible with the Site Editor.' ) );
+	} elseif ( ! $is_patterns_editor && ! $is_template_part_editor ) {
+		wp_die( __( 'The theme you are currently using is not compatible with the Site Editor.' ) );
+	}
 }
 
 // Used in the HTML title tag.
diff --git a/src/wp-includes/functions.php b/src/wp-includes/functions.php
index a3a5e56bfad18..6b237c75899a2 100644
--- a/src/wp-includes/functions.php
+++ b/src/wp-includes/functions.php
@@ -5356,7 +5356,7 @@ function wp_widgets_add_menu() {
 	if ( wp_is_block_theme() || current_theme_supports( 'block-template-parts' ) ) {
 		$submenu['themes.php'][] = array( $menu_name, 'edit_theme_options', 'widgets.php' );
 	} else {
-		$submenu['themes.php'][7] = array( $menu_name, 'edit_theme_options', 'widgets.php' );
+		$submenu['themes.php'][8] = array( $menu_name, 'edit_theme_options', 'widgets.php' );
 	}
 
 	ksort( $submenu['themes.php'], SORT_NUMERIC );