Index: src/wp-admin/menu.php
===================================================================
--- src/wp-admin/menu.php	(revision 51896)
+++ src/wp-admin/menu.php	(working copy)
@@ -202,8 +202,13 @@
 	/* translators: %s: Number of available theme updates. */
 	$submenu['themes.php'][5] = array( sprintf( __( 'Themes %s' ), $count ), $appearance_cap, 'themes.php' );
 
+if ( ! is_multisite() ) {
+	/* translators: Add new theme. */
+	$submenu['themes.php'][6] = array( _x( 'Add New', 'theme' ), 'install_themes', 'theme-install.php', '', 'hide-if-no-js' );
+}
+
 	$customize_url            = add_query_arg( 'return', urlencode( remove_query_arg( wp_removable_query_args(), wp_unslash( $_SERVER['REQUEST_URI'] ) ) ), 'customize.php' );
-	$submenu['themes.php'][6] = array( __( 'Customize' ), 'customize', esc_url( $customize_url ), '', 'hide-if-no-customize' );
+	$submenu['themes.php'][7] = array( __( 'Customize' ), 'customize', esc_url( $customize_url ), '', 'hide-if-no-customize' );
 
 if ( current_theme_supports( 'menus' ) || current_theme_supports( 'widgets' ) ) {
 	$submenu['themes.php'][10] = array( __( 'Menus' ), 'edit_theme_options', 'nav-menus.php' );
Index: src/wp-includes/functions.php
===================================================================
--- src/wp-includes/functions.php	(revision 51896)
+++ src/wp-includes/functions.php	(working copy)
@@ -5141,7 +5141,7 @@
 		return;
 	}
 
-	$submenu['themes.php'][7] = array( __( 'Widgets' ), 'edit_theme_options', 'widgets.php' );
+	$submenu['themes.php'][8] = array( __( 'Widgets' ), 'edit_theme_options', 'widgets.php' );
 	ksort( $submenu['themes.php'], SORT_NUMERIC );
 }