Visual Studio Code Server
Visual Studio Code is a source-code editor made by Microsoft. Features include support for debugging, syntax highlighting, intelligent code completion, snippets, code refactoring, and embedded Git. For more information about the server, see the home page: Visual Studio Code Server.
To start VS Code Server in a CoCalc project, select Servers in the Activity Bar and click the “VS Code” button:

starting VS Code Server from Servers in the Activity Bar
When you click the link to start Visual Studio Code Server, a new browser tab opens with VS Code running as a browser application. All files are in the project, and therefore accessible from any browser.
VS Code server is available in CoCalc.com and the CoCalc Docker Image.
There’s no transparent support for multiple collaborative editing yet.