Thanks, Amber, for the advice about importing from Tinderbox to Scrivener.
Having set this off, I think I must leap to the defense of Tinderbox. It looks like it has a steep learning curve, but you can in fact do the simple and very helpful things first and leave the complicated stuff for later. For example, I like to do an initial brainstorm for an article or book in map view, putting ideas down without worrying too much where they will end up, then make links, find connections with other things I have noted in the past, and then develop a more linear structure using outline view. It is possible to apply agents and rules subsequently do to things with the notes. The real strength for me is the mapping, linking, and connecting with everything else that I have done (I keep all my notes in one file). Others work more on GTD, building websites with Tinderbox, blogging and so on.
Tinderbox is not ideal for drafting complex texts through numerous revisions,keeping things focussed on that task, and providing a good, visual writing environment, which is where Scrivener will come in - although I am a beginner here. In addition I use DevonThink as an archive for collected research material, and will have to go on using Word to send text to editors and publishers, largely because of the reviewing and commenting function.
I must say, I am impressed with the quick responses on the forum and the support of the Scrivener community - a lot like Tinderbox!