Add icon to dropwdown menu

packages/tree-extension/src/index.ts

@@ -24,7 +24,11 @@ import { IRunningSessionManagers, RunningSessions } from '@jupyterlab/running';
 
 import { ITranslator } from '@jupyterlab/translation';
 
-import { folderIcon, runningIcon } from '@jupyterlab/ui-components';
+import {
+  caretDownIcon,
+  folderIcon,
+  runningIcon
+} from '@jupyterlab/ui-components';
 
 import { Menu, MenuBar, TabPanel } from '@lumino/widgets';
 
@@ -50,6 +54,7 @@ const createNew: JupyterFrontEndPlugin<void> = {
     const menubar = new MenuBar();
     const newMenu = new Menu({ commands });
     newMenu.title.label = trans.__('New');
+    newMenu.title.icon = caretDownIcon;
     menubar.addMenu(newMenu);
 
     const newCommands = [

packages/tree-extension/style/base.css

@@ -37,3 +37,7 @@
   flex-direction: column;
   justify-content: center;
 }
+
+.jp-DropdownMenu .lm-MenuBar-itemIcon svg {
+  vertical-align: sub;
+}