Seems like Google services are increasingly harder to manage. Now i want to delete a project ID that was previously created in another test account.
Assuming that I could recreate it in another account. The main reason for this is that the Google+ app is connected/created in this test account and the email address will be shown when someone is confronted with the login credentials.
Google says that this is possible (https://developers.google.com/console/help/):
Deleting a project
Deleting a project from the Console releases all resources used within the project itself. Please note that in order to delete a project, you must first disable billing on the project. Additionally, please note that the time it takes to delete a project may vary based on the number or kind of services in use within the project.
When I go to billing, it shows that no billing profile has been set up.