First, you need to enable this functionality by setting a preference. To do that, go to main menu option:
Tools -> Options -> Preferences
If not already checked, check the box corresponding to “Append a short random string to Title on Duplicate”, as shown in the screenshot above.
If you had to check the box, ensure you Save your changes.
Close the Manage Preferences window.
Now, that the feature has been enabled, when you duplicate any listing / listing template, (you can select multiple), the title of the original listing will be appended a short random string in the duplicated listings.