Update on February 27, 2020:
Duplicate Post plugin does not seem to work in a reliable manner.
Therefore, it is recommended that you copy all the shortcodes from the Template/Page (click on + Shortcodes in the edit screen) and paste them into your new Template/Page to duplicate them.
Here’s a quick video on how to use Duplicate Post plugin to duplicate/clone templates and Reusable Parts in Oxygen: