Adding animation effects to your submenus is an effective way to attract customers' attention. In this post, let's walk through quick steps on how to apply animation effects to the submenus in Ninja Menus, an easy and powerful Magento 2 mega menu extension.
https://www.magezon.com/magento-2-mega-menu.html

Supposed that you've already created a menu using Ninja Menus.
1. Open the edit page of the menu, then open Menu Builder section.
2. Hover over the menu item containing the submenu you want to add animations. Then click Edit in the drop-down list to open settings of this menu item.
3. Open Submenu tab. Then choose the effects when the submenu appears and disappears from Animation In and Animation Out drop-down list. You can also set the Animation Duration (in seconds).

Remember to save after finishing.