We should have a button to append a track to the play queue as it would save time and make it easier to quickly add more tracks to the queue. Perhaps we can bring back the '+' icon since we have a new icon for saving tracks and it is a good symbol to represent the action.
Thanks for bringing your suggestion to the Community! It's Ideas like yours that help the Spotify experience be the best it can. I've marked your idea as a New Idea and a repost of this Inactive Idea 🙂