Developed an External Editor Focus Cell API for the marimo-team/marimo repository, enabling external editors such as Neovim and Vim to programmatically scroll the browser to a specific notebook cell by ID. This feature was delivered through a new POST endpoint and a dedicated FocusCellRequest model, with comprehensive tests to ensure reliable synchronization between editor and browser. The implementation involved modifying server-side components using Python and JavaScript, with a focus on API development, testing, and WebSocket integration. This work enhanced cross-tool collaboration and improved developer workflows by supporting precise navigation and seamless integration between marimo and external editors.