There is no trick, you squeeze it and it comes off. Nissan isn't the problem, either the clip is broken or there's all kinds of build up seizing it together. Spray some pb blaster on it and use some strength to pull it apart. If the clip is broken get a small flat head and try to pry it open.
Don't be naive and blame a car maker for a common issue any old, high mileage vehicle has. If this minute issue is enough to turn you off on the car you should probably sell it.
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