If you set the preference “Insertion position in MindMap” to “Auto-grouped by Table of Contents” the note tiles will be contained in “frames” defined by titles of the chapters/sections. That also works in the outline and is very handy in both views to give notes a context.
Unfortunately the “frames” are considered as notes and so they appear also in the folder exported for DevonThink where they don’t make any sense. They’re just almost empty RTF files (containing only the title of the chapter/section and a MN3 link) and ends up polluting the real notes files (and burdening DevonThink searches).
How about avoiding to include the “frames” in the folder exported for DT?