Access nested Value in folder.yaml

I know that i can customize the columns of a collections index-page (in the cp) by adding the following to the folder.yaml in question:

columns:
   - label: seo
     translation: SEO

This would create a column called "SEO" and display whatever is stored in my collections fieldset for the "seo" key.

My collections fieldset for the "seo" key looks like this:

fields:
  seo:
    type: grid
    display: SEO
    fields:
      meta_title:
        type: text
        display: Meta-Title
      meta_description:
        type: textarea
        display: Meta-Description

Since "seo" is a grid with multiple fields, all the control panel outputs is:

[object Object]

Can someone help me understand how to access the values of "meta_title" and "meta_description"? All I want to do ist something like...

columns:
   - label: seo.meta_title
     translation: SEO

... but that doesn't work :(