MarginNote has addressed nicely the unmaneageability of working with the full content of highlights in its mind maps with the option to view questions only.

However, its exports to MindManager / iThoughtsX still render unworkable huge mind maps of large nodes which mix title and content.

To be able to work in iThoughtsX with my titled extracts from read books in MindManager, I would need mind maps with nodes that show only its titles. Their text contents and notes should go into the notes panel of iThoughtsX.

By the way, I believe OPML also has a _notes or _note field which is used by the nice outliner from http://www.topoftree.jp/en/tree/ for a similar purpose.