Hello, I’m Quinn, and I’m here to help.
I’ve run into this issue myself, and no matter how I troubleshoot it, the “Delete” or “Remove” option doesn’t always appear. Since your concern is about duplicate songs, I recommend installing a Duplicate Cleaner from the Microsoft Store. You can choose whichever one suits you best, and it should save you from having to remove duplicates manually.
As for your other question: Windows Media Player 10 isn’t supported on Windows 11. Instead, you can use Windows Media Player Legacy (version 12), which is already installed on your system as an optional feature. It offers a similar experience, and the Delete option does appear there.