Oh, sorry, @Claire_Franklin, I just reacted to the title of this topic “Mark a task…” Now reading the thread I see the confusing mess of discussion between task and project asks. I’m going to see if I can clean it up between this current thread for tasks and this other one for projects.
EDIT:
FYI I moved all of the posts that were in this thread but were discussing project status into this other thread: Add a 'Not started' project status