Try set overflow options explicitly

Author: jtpio

packages/lab-extension/src/index.ts

@@ -77,7 +77,10 @@ const launchButtons: JupyterFrontEndPlugin<void> = {
     const { commands, shell } = app;
     const baseUrl = PageConfig.getBaseUrl();
     const trans = translator.load('notebook');
-    const menubar = new MenuBar();
+    const overflowOptions = {
+      overflowMenuOptions: { overflowMenuVisible: false, title: '' }
+    };
+    const menubar = new MenuBar(overflowOptions);
     const switcher = new Menu({ commands });
     switcher.title.label = trans.__('Interface');
     menubar.addMenu(switcher);
@@ -134,7 +137,7 @@ const launchButtons: JupyterFrontEndPlugin<void> = {
         'Notebook',
         'interfaceSwitcher',
         panel => {
-          const menubar = new MenuBar();
+          const menubar = new MenuBar(overflowOptions);
           menubar.addMenu(switcher);
           menubar.addClass('jp-InterfaceSwitcher');
           return menubar;

packages/tree-extension/src/index.ts

@@ -80,7 +80,10 @@ const createNew: JupyterFrontEndPlugin<void> = {
     const { commands } = app;
     const trans = translator.load('notebook');
 
-    const menubar = new MenuBar();
+    const overflowOptions = {
+      overflowMenuOptions: { overflowMenuVisible: false, title: '' }
+    };
+    const menubar = new MenuBar(overflowOptions);
     const newMenu = new Menu({ commands });
     newMenu.title.label = trans.__('New');
     newMenu.title.icon = caretDownIcon;
@@ -103,7 +106,7 @@ const createNew: JupyterFrontEndPlugin<void> = {
         FILE_BROWSER_FACTORY,
         'new-dropdown',
         (browser: FileBrowser) => {
-          const menubar = new MenuBar();
+          const menubar = new MenuBar(overflowOptions);
           menubar.addMenu(newMenu);
           menubar.addClass('jp-DropdownMenu');
           return menubar;