The built-in coupon and price comparison tool in Microsoft Edge (Chromium) adds a new shopping experience within the browser window by displaying coupon codes when you visit any shopping site. The feature is still hidden under a flag as an experimental feature to Edge Insiders and hence you won't find it in the stable release.
Now, as part of the unified code base, Microsoft is moving the feature to the Android version of the Microsoft Edge browser. If you are running Edge Canary build on Android, you can experience the same right now. For more details, continue reading.