Youtube features a new dedicated data saving page.

YouTube features a new dedicated data saving page where every data saving related setting is bundled up.

As shown above, the new data saver menu has all data saving related settings on a single page which includes the following toggles data saver mode, reduce video quality, reduce download quality, only down over Wi-Fi and unrestricted mobile data, upload over Wi-Fi only and muted playbacks in feed over Wi-Fi only.

Further, YouTube also showcases a featured banner on the home page as follows.

Further, this feature is spotted by myself on YouTube Android version 17.20.33 and you can download it from APK Mirror and try your luck as well.