Gerrit users on large projects may accumulate many dozens of open patches awaiting review. The only ways to remove a change from the dashboard view are to submit the change, abandon it, or explicitly remove yourself as a reviewer.
I would like to be able to "archive" (to use the Gmail terminology; you might prefer "hide" or "dismiss") a change from the dashboard if I am not planning to review it (or if I have already reviewed it and do not want to see it again until it is updated). Why not remove myself as a reviewer in this case? I don't actually want to unsubscribe to this change—if someone comments or bothers to resubmit it, for example, I'd like to get a ping—but I don't need it in the way of changes that still need my actual attention. I'd also like to be able to recover it with a query like [reviewer:$USER].