What method to use for capturing thoughts is a highly subjective subject: some write outlines, some just a simple text, and some prefer mind maps. DEVONthink supports text and very simple outlines (e.g. using rich text lists), but not (yet) mind maps. Some options are:
Some of these apps come either with a Quick Look plugin that allows DEVONthink to preview them when you add them to your database or at least write PDFs that you can add to your project files in DEVONthink.
There has also been a discussion on our user forum that might be interesting for you in case you’re interested in using a mind mapping app with DEVONthink. Click here.