Adding content below Subnavigation?

# Support
## Description

I wonder why the templates with subnavigation do not allow adding content below this subnav.
On larger displays, it's a perfect place to enrich page content with add'l details that are good to know but also can be left off (e.g. add'l "story of my life") on smaller screens.

With having that issue I wonder how to adjust the templates best in order to enable the possibility to add content there :)