Most streaming music services generate a "Liked Songs" playlist, including your favorite tracks or library tracks in a dedicated playlist.
While we are not displaying this "playlist" directly under the "Playlists" tab on Soundiiz, these songs are displayed under "Tracks" in the Soundiiz left panel.
Using the "Transfer" tool, you will be able to move them to the "Liked Songs" playlist in the destination platform (or in the Library, depending on the service) quickly.