Adding new toolbar menus in Unreal

UnrealMenuExtender.cpp

/* Continuation of answer to this question: 
https://answers.unrealengine.com/questions/587450/how-to-make-a-simple-menu-in-the-editor-with-plugi.html */

void FMyPlugin::StartupModule()
{
  FLevelEditorModule& LevelEditorModule = 
  FModuleManager::LoadModuleChecked<FLevelEditorModule> 
 (LEVELEDITOR_MODULE_NAME);
  TSharedPtr<FExtender> MenuExtender = MakeShareable(new FExtender());

  MenuExtender->AddMenuBarExtension(
    "Help", 
    EExtensionHook::After,
    nullptr,
    FMenuBarExtensionDelegate::CreateRaw(this, &FMyPlugin::AddMenu)
  );
  LevelEditorModule.GetMenuExtensibilityManager()->AddExtender(MenuExtender));
}

void FMyPlugin::AddMenu(FMenuBarBuilder& MenuBuilder)
{
  MenuBuilder.AddPullDownMenu(
    LOCTEXT("MenuLocKey", "My Menu"),
    LOCTEXT("MenuTooltipKey", "Opens menu for My Plugin"),
    FNewMenuDelegate::CreateRaw(this, &FMyPlugin::FillMenu),
    FName(TEXT("My Menu")),
    FName(TEXT("MyMenuName")));
}

void FMyPlugin::FillMenu(FMenuBuilder& MenuBuilder) {
   // Fill it same as in the accepted answer
}