Custom Templates feature is introduced in this article.
Let's consider the usage of Custom Templates in Prestashop. Here are some sample steps to follow:

1. Open the Templates list and select Add template to add a new
   custom template or Duplicate template option to duplicate an
   existing template.

2. Specify the template type. For example, let's add a new Page Template:

   

3. Enter the template title and save changes by clicking "OK".

4. Now there are two Page Templates in the theme, the newly added template is available in the Templates list. Select and configure it in the way you want.
5. Save changes to the theme and go to Prestashop admin panel.
6. Navigate Billion Themler >> [choose the theme] >> Template Settings and assign the new template to a page/pages. In our example the "Page 2" template can be set for CMS Pages:

Now CMS Pages use the new custom template.

See also:

Templates
How To Create And Use Custom Templates