Once a project is added in your Dashboard, it is also added to the dashboards of Rank Tracker and Site Audit. So it is important to keep in mind that deleting a project from the Dashboard, will also remove the project from the other two tools too.
Before proceeding, ensure that you also no longer require the project's data in Rank Tracker and Site Audit.
Here how to delete a project:
Scroll to the project you would like to delete and click on the 3 dot menu:
2. Select "Delete" from the drop-down to see the "Delete project" option:
Check all 3 boxes to confirm the data will be deleted. After the confirmation, you can delete your project.