Currently, to duplicate the project, you have to select one page at a time in the Base box to copy and migrate. Here are instructions on how to copy and paste the page.
First, open the layers panel on the right side of the screen.
Then select Base at the top in the Layers panel and copy it with ⌘+C or Ctrl+C.
Please use ⌘+V or Ctrl+V to migrate each page in another project you are moving to.