Thanks for the explanation, but it is still a bit confusing.
I have changed front matter to this state:
menu:
templates:
title: "templates"
docs:
title: "Documentation"
parent: "templates"
Now when i do {{ range .Site.Menus.docs }} i can get the Docs menu item as a child, but the parent field is empty:
<ul class="top-level">
<li>
<a href="#"></a>
</li>
<ul class="sub-menu">
<li>
<a href="/blog/dota2-guide/">Documentation</a>
</li>
</ul>
</ul>
And if i do {{ range .Site.Menus.templates }} i get only Templates menu item as parent, with no children