Marta here, from Trello Support.
Right now, that feature isn’t available within Trello although I understand how it would be nice to have the card added to the top of the list. I’ll pass your interest in this on to our team for consideration—let me know if there's any additional info you'd like for me to send their way.
If you're curious about how our team decides on what requests we work on, this article gives some insight into that process: http://help.trello.com/article/724-submitting-feature-requests-for-trello
To see what features our devs are currently working on, check out our dev board at http://www.trello.com/dev. Our mobile boards are available at https://trello.com/b/5tj4qAvo/trello-ios-app and https://trello.com/b/ud59t1fL/trello-android-app, and serve the same purpose for our mobile apps.
Please let us know if you have any other questions or concerns, and have a great day.
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