Could this be the Surface Duo 2?

Forget about dual-screen devices, the future is triple-screen laptops and phones. At least, that’s what Microsoft seems to think based on a patent (via Windows Latest) that turns the hinge of a dual-screen phone into a third display. The device looks a lot like the upcoming Surface Duo but with an extra slender screen.

Microsoft says the hinge could be used as a bridge between the two main displays so you see one continuous image.
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https://www.laptopmag.com/news/microsoft-surface-foldable-phone-could-have-three-screens