Nested indexes that encode a root index that point to categories, which contain sorted long form articles, are called magazines in Decent Newsroom.
This is a demo magazine:
https://decentnewsroom.com/mag/newsroom-magazine-65b0d6You can create your own at
https://decentnewsroom.com/magazine/wizard/setup There’s a multi-step form that asks for details about the root index and the categories. Then you can add articles, or leave the categories empty. On the last step, you’ll be given events to sign.
The structure can be edited anytime, later on. The events are parametrized replaceable.
You’ll be able to add articles into the categories in the wizard, or from each article’s page, if you log in. For logged in users there’s a dropdown that lets you choose the category to place the event into, and a replacement event is generated for you to sign with the article included.