Hello,
Thanks for the great question. Probably the easiest way to accomplish this is to save a custom Block in your Post and Page Builder Block Library.
Using this method, you would edit the page that you want to duplicate, select all content and copy it to your clipboard. Then, navigate to Post and Page Builder -> Add New Block and paste the content into your new block. Give it a name that you can easily remember, and then you’ll be able to find it from the Add Block -> Block Library selection.
Another way to accomplish this is with a plugin like Duplicate Page.
I hope this helps!