First, please read this How To Guide. Brand, Company, and Group Admins are able to archive templates that are no longer in use.
Now, let's try it out! Head to the template details page by clicking on the name of the template, and then check the box next to Archived. By checking the Archive checkbox, the template will no longer show up in your active templates list, helping prevent clutter.
Archiving a template also removes it from being available by your Sales Agents as well as Companies and Groups (if you archive it at the Brand level). To access your archived templates at a later date, simply select the Archived status filter on the left side of your templates page.