Let me see How many Developers want to stop the Xcode's cursor blinking!!!

There’s an undocumented-but-easy-to-search-for global defaults setting that controls cursor blinking in various apps in macOS. It does work for plain text fields within Xcode, but seems to have no effect in the main editor. You could submit a Feedback to request the Xcode editor respect this setting, or to just add a cursor blink setting directly in Xcode.