Sitefinity 4 is a web application and differs from Sitefinity 3 which is a website project. Note the link to the documentation you provided is for Sitefinity 3.x. Here is a link to Sitefinity 4 documentation
Sitefinity 4 saves pages in the database and you can not edit the page or browsing its code. You can create a template for a page based on master page and use it to create pages. With the master page you have access to how the page is structured. Here is the documentation
on how to create a master page for Sitefinity 4 and use it in your project. Save your master page in App_Data/Sitefinity/WebsiteTemplates/name_of_template/App_Master/...your master pages. Create the folder structure I mentioned in Visual Studio and add your files there. Then you will be able to edit the master page directly in Visual Studio.
the Telerik team
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items