One of the best ways to express interest in having a song added to Spotify would be to try to contact the label and/or artist, as they are the ones ultimately responsible for approving whether something is added to Spotify or not.
Also, you can check out this form to forward your specific requests to the Spotify team just so they are aware of the interest.
Hope this helps 🙂
Billy-JRock Star 22
Help others find this answer and click "Accept as Solution".
If you appreciate my answer, maybe give me a Like.