Heynote
A dedicated scratchpad for power users
...Users can write and format code with syntax highlighting for numerous languages, including Python, JavaScript, JSON, and Markdown. Heynote includes a calculator mode, currency conversion, inline images, and multi-buffer searching. Its editing tools support multiple cursors, automatic formatting, and customizable keyboard shortcuts. Available for Windows, macOS, and Linux, it combines the simplicity of a scratchpad with specialized development utilities.