Funny enough, two years since making it, I'm still working on the one liner (creator of Dendron here).

The current one liner: dendron is an open source, developer focused note taking tool that lets you quickly find and organize your notes in vscode using flexible hierarchies.

Given a few more lines, I would add: what IDEs do for programming languages, we want to do for knowledge - that is to say, give you the tooling to manage large amounts of it using concepts like refactoring, lookup, and schemas (think of this as type definitions but for the structure of your notes)

Obsidian or Logseq functionality in a VS Code extension.

Hierarchical note taking as a VSCode Extension.