Win10: remove optional language feature

1. Navigate to Windows Settings > Apps & features > Manage optional features
2. Locate the optional feature you want to uninstall, select Manage
3. It will switch to the Region & language screen which is quite confusing. Under the language list, remove the undesired language
4. Now navigate back to Manage optional features, the previously selected feature should be removed

Ref:
Cannot remove languages from Optional Features - Microsoft Community