Here is how I am currently getting things rendered only in nested sections and not main sections.
https://discourse.gohugo.io/t/list-pages-of-sub-sub-folders/9436/11?u=onedrawingperday
And here is how I am building a breadcrumbs navigation on a single page that renders the link to the parent nested section.
https://discourse.gohugo.io/t/implementing-breadcrumb-navigation-in-hugo/1048/42?u=onedrawingperday
Just make sure to replace .URL with .Permalink for the links in the above linked snippet.
I think that you will be able to get what you need done with the snippets in the links I posted.
Also you should be able to access the parameters you need from the nested section _index.md