Make copy/clone of local website

Copying a site is not always as straightforward as copying your files. Is your site using a CMS like Wordpress or any database for that matter? If you so you will need to go into your database and copy that as well and you may need to perform some manual edits in the database to update paths from the old location to the new location even if it's on your hdd.  

Safest way is to use your computer's operating system (Win File Explorer or Mac Finder) to copy the folder to a new physical location on your hard drive.   Example, C:\MyNewSite\.

Then Create a new site definition in Dreamweaver.  Site > New Site...

This ensures that whatever changes you make will have no effect on the old site.

Hope that helps.

To get what you're asking, you can right-click and access the Edit menu and the sub-menu Duplicate, which will clone the selected folder (or item).

However I will have four remarks :

• The way you describe the context seems to indicate that you have not defined a site in DW... because as soon as you define a site, you don't see anymore the folder where the site is located, which becomes the root folder https://helpx.adobe.com/dreamweaver/how-to/define-a-dreamweaver-site.html
• So, if you want to clone the root folder, the one that contains the whole website, it will not be possible from within DW, but only from Mac OS (then, you will need to define a second website).
• Anyway, the functionality you seem to be looking for is offered by a third party GIT technology... which fortunately is available within DW https://helpx.adobe.com/dreamweaver/using/git-support.html
• Before using GIT, it is still necessary to understand the principle of operation of GIT. For that, I recommend you to start by the reading of this very didactic article https://medium.com/data-management-for-researchers/the-philosophy-of-git-8e00f3ab61ef then, continue by a second one which is emitted directly by the basic team https://www.git-scm.com/book/en/v2/Getting-Started-What-is-Git%3F