Modify settings for extended layout with columns?

Kirby 3 Questions 🤔
1

If I use a “simple” layout only with tabs, it is easy to modify every element of the layout in the extending blueprint.

If I want to change the headline of the image field in the sidebar of this layout:

tabs:
  content:
    label: Inhalt
    icon: text
    preset: page
    sidebar:
      images:
        extends: sections/images

I can do just something like that:

extends: layouts/mylayout
tabs:
  content:
    sidebar:
      images:
        headline: New headline

But how do I address elements in columns of a column based layout?
In my case I try to build my own pages-layout based on the blog example using 2 cols for unpublished and published elements but have to modify the template setting when extending from it.
https://getkirby.com/docs/reference/panel/samples/blog