Click the "HTML" button in the post editor toolbar. Tumblr switches the post editor to HTML mode. Scroll to the section of code that contains text or the object that you want to center.

If you’re browsing some code in a repo ... and choosing a default language for the editor. There are a lot of options you can set via the editor properties. Many let you customize the editor ...

Visual Studio Code, or VS Code for short, is a lightweight but powerful source code editor that runs on your desktop and is available for Windows, macOS, and Linux.