DiaGrammar for Windows (by Redlake Tech)

From Website:

Facts. Data. Diagrams. Stay informed. While getting DiaGrammar ready for prime time we decided to create and release a set of diagrams that depict some basic processes for controlling COVID-19. View or download to spread the facts, not the virus.

Whether you design languages and DSLs, parse or document data formats, or publish APIs, DiaGrammar is your new best friend. Users want to understand your design quickly. Diagrams foster understanding, communication, and adoption. Today’s stakeholders demand that designs are thought-out, documented, and tested. You need to look professional. More than that, you need to be professional.

Don’t hack, design. Don’t hope, test. Don’t guess, understand. Then show everyone what you’ve got. Live coding is the best, most productive way to do this. You get immediate feedback, see and fix problems instantly, and work as fast as you can think.

-- Comment: Works a little bit like an outliner, but allows for much more complex visualization.