Most sprints priorities will change a little bit as time goes on and it will be appropriate to remove a ticket that was added previously. Likewise, if a sprint is over subscribed some tickets may roll over into the next sprint.
When this happens, they will often be put in the parking lot in Aha to be re-planned. It would be nice if this move to the parking lot resulted in an automatic move to the Icebox in Pivotal right now -- currently, team leaders have to do both tasks consecutively.
Thank you for the idea. Given the low volume of support for this idea, we do not have plans to make updates in this area at this time. We hope you can understand.