You might have found something already but I was just looking into this issue as well, and found close one in extension.
https://addons.opera.com/en/extensions/details/moregestures/?display=en
It's RMB+Drag Up instead of what used to be, but I guess I'll just have to adjust to it.
Latest posts made by iyamayoshi
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RE: Opera 16.0 - Mouse GesturesOpera for Windows