I think that this is a good idea as well, and there is currently a live idea in the Ideas Exchange of the Spotify Community for the ability to select multiple tracks on the mobile app, which could be used to clear the entire queue at once. You can feel free to add your +VOTE for this idea here, as well as to add your feedback in the comments section. The higher the number of votes an idea gets, the more likely it is for the idea to be implemented; and you can read more about how feedback on Ideas reaches Spotify here.
I hope this helps, and let us know if you have any other questions.
Have a good day!
TreyAnastasioRising Star 20
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