The Spotify channel allows you to feature songs that have not yet been released for their officially curated playlists.
To do this, you must go to your Spotify account (Spotify for Artists in the case of artists and Spotify Analytics for labels) and select the track you want to present for lists. The channel's editorial team will take your proposal into account and decide whether to include it or not and on which list. The final decision is always left to the professional team at Spotify.
It is recommended to make the request a minimum of 7 days before the launch of the track and to enter all the possible information about the song. You can check more details in this Spotify blog post.