Production queue editing

In the city production queue, i can't find a way to remove items, even those not under production yet, just queued. I can accept that a given stuff should be finished after started, no way to turn production invested in a settler suddenly changed to a granary.

However, this should not apply to units not yet in production, i should be able to remove them from the queue and put something else instead.

Also the item under production should be able to get replaced, but with a sacrifice, either full production, or 70% of it etc.