how to keep phone screen Off while in Dex mode??

[BoonKing]

My problem is Dex mode. If phone turns off with screen sleep timer set, every text you will start to input with keyboard.. Screen will turn on again..

So how to keep phone screen Off while in Dex mode?

Thanks 

[khtannnnnnnnnn]

Under Samsung dex settings, keyboard option - in there you should fine option for display keyboard on device screen or something.

This should stop your phone screen turning on. i hope

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EDIT:
It's called on screen keyboard location