Notable is a markdown-based note-taking app with no WYSIWYG or proprietary formats; it includes many editing options and a refined UI.
Notable notes are written in GitHub Flavored Markdown. You can also write KaTeX expressions, Mermaid diagrams, and so much more. Notable provides you with a powerful Markdown editor; it's the same one VS Code uses. This means features like multi-cursors, a minimap, and best-in-class syntax highlighting are built-in.
Any notes and attachments get stored on your disk. This fact makes it extremely portable and powerful: you could edit your notes using your favorite editor, have them synchronized via Dropbox, run Git on them, run a regex-based search and replace them, etc. It additionally lets you choose light and dark themes to suit your surroundings and preference.