How do I mark a project complete?
Once your project has wrapped completely (all Diary and Live missions are done), mark it complete from your home page by clicking the box icon in the top right corner of the project section box (circled in green in the screenshot below).

Marking your project complete closes all missions and screeners in the project (if they're not already closed) and removes the project from your Home page's main project lists.

Completed projects will still be visible and accessible, but out of the way, in the Completed projects list.
Note: Completed projects cannot be un-completed.