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Yes, aside from bulkhead and exit row seats, all armrests on the aisles lift up.

There is a small catch towards the back of these armrests. It is underneath, about 5cm from the base/hinge. It is normally a blunt alloy hook protruding about 1cm. You hold the armrest steady, slide the hook forward and lift the armrest up. This can be fiddly as the mechanism is restrained by a strong spring. Don't try to lift the armrest until you have moved the hook forward at least 1cm.