TomboyTools
This is a small FPC/Lazarus project that provides some tools to help manage a Tomboy/tomboy-ng note collection. Things like importing and exporting, perhaps in in bulk. Exporting as plain text, Markdown, Man Page and HTML (following links).
You can export and export notes, one by one, all in a particular Notebook or all in a directory. This tool should work fine with Tomboy, tomboy-ng or, perhaps, G-Note.
Binary install packages for Linux and Windows are available from the Release Page
If you have any problems, please report them here.