@death7991 After trial and error trying to solve the problem, I managed to delete the vehicle I wanted to get rid of by using the "Delete" tab under the "Modify" tab. It still didn't turn on the "delete" tab in the Scene nodes browser, which is more convenient but, to my surprise now the "delete" option magically shows up when I mouse right-click on the object. Before I was only getting one single option,"Reference", but now I get other options when I right-click on the vehicle I want to delete, now I get Copy, delete and flip in the "Edit" sub-category. Thanks for your suggestion anyways.