I know I'm not dumb however when something stumps me I think maybe I am! I have an accumulation of drafts that I have started, not completed and probably not relevant if I go back through them. ...
Click on your drafts 'folder' (usually just below your 'discussions' folder) ..... it should show any 'drafts' that weren't completed or may have changed between starting & submitting!!
Just click on the 'x' in the top right hand corner of each draft - and it will be deleted!!