Copying is available to paid plan users only as there's a limit of 1 CJM, 1 impact map, and 1 persona per user on the free plan. So, if you're the one with a paid plan, you can copy your persona:
From the Dashboard page: select a persona and click on the ‘Copy’ action…
… or hit the ‘Copy’ action in the Actions column.
From the Tag page.
Copying on this page works the same way as on the Dashboard.
From the document page.
After you click ‘Copy’, you’ll see a popup prompting you to select a target Workspace and project.
You can also assign a tag to the persona copy from the list of tags of the target workspace.
That's it, folks!