How to display nested data in Vue table?

Question

Vue.js

I'm using ElementUI .
There was a need to organize nesting inside the table cell. I can't figure out how to do it at all. Here is https://jsfiddle.net/3nhb79qc/
Inside the cell, a new column should be with data.
I want to do something like this:

Answer 1

didn't finish it... but you get the gist