Q:

How to add an external link under a page in Kentico? 

We’re using Kentico 11.0.26 with MVC. 
I need to add an external link under a page. 
In content tree it should look something like this:

Page A

Page A1
Page A2
https://www.www.google.com/

The problem is that when I click the + button in Pages application, I only see page types, and there is no option to add a link. 

A:

You could create a new content type to represent an external link and put that into your content tree.   This would then also give you options to set additional properties of the link such as target and title rather than just a URL.