Dex is a very productive mode.  Why there is still no portrait mode for dex?

It's very convenient to use these flagship smart phone with a portable screen.

BUT

Dex can not show portrait A4 pdf file. Because it can't display in portrait direction😔.

Dex can not use full screen to play vertical game.  Because it can't display in portrait direction😔.

If we turn off dex but use mirroring output, there are still large black block and only a small part in center display portrait app. 

Why can't let dex have a landscape/portrait switch button?

Portrait mode can significantly enhance productivity and usage of dex mode.

Please, is there any method to rotate apps in dex ?

And please Samsung develop team to enhance dex supports both landscape and portrait in future release