How to get defined display names (id) from selected view?
This will loop through every page display and set a menu item.

  $view = views_get_view('VIEW_NAME');
  foreach ($view-&gt;display as &amp;$display) {
    if ($display-&gt;display_plugin == 'page') {
      // Add an if or switch statement here to check $display-&gt;id
      // so you can set different menu items for each display.
      $display-&gt;display_options['menu'] = array(
        'type' =&gt; 'normal', // Menu item type.
        'title' =&gt; t('Menu item title'), // Menu item title
        'description' =&gt; '', // Menu item description
        'name' =&gt; 'main-menu', // Menu name
        'weight' =&gt; 0, // Menu item weight
        'context' =&gt; 0, // Not sure off the top of my head what this is for.
      );
    }
  }


However this will set the same menu item for each display.
You will need to check the $display->id for each one so that you can set a different menu item for each display.

Also, that example sets a normal menu item.
If you want a local task or default local task it will be slightly different.

...also, why do you need to do this? why not add the menu item via the views UI?