I have rarely had occasion to do this, but it just happened and I could not figure out how it’s done. Just moving the project up or down as levels in the main outline doesn’t work – it still retains its “Project-ness” with (for example) the Parallel/Sequential/Single Action project type choices. Dragging it to the Inbox doesn’t work either.
I ended up just creating a new task and pasting my Note content into it. Is there a direct way to convert these?