Where I work, this isn't how UX and engineering interact at all. In fact UX never actually makes direct changes to the code at all. They are no longer part of the engineering org. Instead, they are part of the product org. They work with product to envision what the UI will look like using tools like Figma. They also to UX analytics using tools like Pendo.io to better understand what changes need to made to improve the user experience.

Then they create design systems using tools like zeroheight, which defines the composition, look and feel of all of the UI components. The developers collaborate with designers with tools like StoryBook which actually creates to code for the UI components. The designers test and approve the components before they ever go into the application. Then the developers compose the UI of the application with the UI components that come from the design systems. There's nothing to clean up. If there was, engineering would clean up their own mess.