To rename a project within the Photos.app, perform the following steps:
Go to "My Projects" and click on the project you wish to rename.
You can now rename the project.
Another option to rename a project is via the context menu.
Please note that the project must be closed before you can rename it.
Duplicating a project can sometimes be useful, for example, if you want to edit the project but retain a copy of the original version.
Duplicating a project with "Apple Photos" is simple:
Go to "My Projects" and right-click on the project you wish to duplicate.
In the context menu, select "Duplicate project"
If you no longer need a project, you can delete it in the same way.
Go to "My Projects" and right-click on the project you wish to delete.
In the context menu, select "Delete project"