Creating a new template is only available for Online Store 2.0.
All themes come with a default template for each type. Resources use this default template if you don’t explicitly set an alternate template.
When you edit a template, it affects all pages using that template. To display some pages differently, create a new template based on an existing one in your theme. The new template will have the same sections, which you can then edit without affecting other templates of that type.
Step by step on how to create a new template
From your Shopify admin, go to Online Store > Themes
Find the theme that you want to edit, and then click Customize.
Use the Template drop-down menu to select a template. Click + Create template.
Give your template a unique name.
Using the Template drop-down menu, select which existing template you want to base your new template on.
Click Create template.
Assign page to new template
From your Shopify admin, go to Online Store > Pages
Use the search filter to locate the page that you want to change, or click on the page from the list of existing pages.
In the Online store section, use the dropdown menu to select a new theme template to apply to the selected page.
Click Save.
Now, you can apply the changes you want to this template in the Shopify theme editor, and be assured that other products and pages with a different template won't be affected.