noticed this in trawling the Omnifocus frums for tidbits on what works. I suppose it's obvious but "brute force" might have meant typing in those tasks again whereas in fact when I had the same problem it was a cinch.

In planning mode I just created folders with exactly the same names as the projects and then drag 'n dropped the contents of the projects into the corresponding new folders. Using the context menu in the LHS pane I then just 'delete'ed the empty projects. For a small number of projects, "hoisting' them in this way is easy.

...Ian.