You can remove the portal project from Workflows on the Delete portal page. Removing the project does not affect the source of the portal.
Navigate to the Settings > Delete portal page for the project you want to remove.
Select Delete. This opens the Delete portal dialog with a warning message.
In the dialog, enter the portal name and select Delete portal to confirm removing the project. Select Cancel to exit the dialog if you don't want to delete the project at this time.
After successfully removing the project, you are automatically redirected to the Portals page in Workflows.