Dendron is described as 'Open-source, local-first, markdown-based, note-taking tool built on top of VSCode. It supports all the usual features you would expect like tagging, backlinks, a graph view, split panes, and so forth' and is a popular Note-taking tool in the office & productivity category. There are more than 100 alternatives to Dendron for a variety of platforms, including Mac, Windows, Linux, Web-based and iPhone apps. The best Dendron alternative is Obsidian, which is free. Other great apps like Dendron are Anytype, Notesnook, Zettlr and Zim.
Another VSCode-based solution for note-taking using local markdown files. Unlike Dendron it's not focused on hierarchies and relies on links and backlinks for structuring notes.