A deleted project is removed from user's workspace and marked as deleted in design time repository. All users can see that a project is deleted. Physically, it still remains in design time repository.
To delete a project, proceed as follows:
Perform one of the following steps as required:
In the project tree, select the project and, in the right pane, click Delete.
In the project tree, select Rules Projects and, in the right pane, next to the project name, click Delete 
.
In the confirmation window, click Delete.
Deleted projects can be restored by using the Undelete button.
To make deleted projects visible uncheck ‘Hide deleted project’ checkbox on the filter pop up window and click ‘Apply’.