[Inkpad 3] Adjusting brightness in reading mode does not work.

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Hello, recently I've bought a new Inkpad 3 after my old one broke. I noticed that this new one is missing a feature that gave you the ability to change brightness while in reading mode using swiping gestures. At first I thought I just needed to bind it in Settings\Personalize\Key Mapping\ but there is no such option. I use this feature quite a lot since I don't like the auto adjusting setting and I often read under different lights (in the bus, at work, at home etc.), so the lack of this feature is really irritating. Does someone know how can I turn this feature on ?

For those that don't know what I'm talking about, I included a picture from the official manual where this feature is explained.

Thank you.