How to add animation on v-if in dropdown (vuetify)?

Question

Vue.js

Hello! When you click on the v-list-tile, the menu drops out and the content is displayed (v-if is responsible for the display). How can I make the menu open as smoothly as it closes?
https://codepen.io/anon/pen/jdLYPg?editors=1010
Thanks!

Answer 1

Or maybe no v-if is needed here?

Answer 2

https://codepen.io/nvdfxx/pen/NovzRR