I've been looking at static site generators to build a very simple set of note pages. All I want is a menu on the left with categories and pages, pages in a simple format like Markdown or WYSIWYG editor, and a dark theme. Output should be static HTML/CSS, no need for Javascript or fancy features like search or in-page navigation.

I have tried mkdocs, but I can't get the navigation menu to work how I want it. I just want category headers with indented pages in a list. I tried the two bundled themes and Material, they don't seem to support this. In Material the side-bar is collapsed into menu icon at 1220px which is too small for me, and I couldn't find any information on changing that behaviour.

I looked at Jackyl, but it seems overly complex and blog oriented. I looked at 11ty but it seems similar to Jackyl. Middleman seems somewhat promising, but I can't see from the docs if it does what I want and finding example sites isn't easy because the name is to generic. The themes I found all look like blogs, not what I want.

What is a suitable application for this? Formal requirements are that it must be open source. Ideally Windows compatible, but I can run it under Linux if needs be.