Enable assistant menu, this is best way ,by this option you can also perform other important task such as screen off, navigation, sound, screen rotation, power off menu, notification panel and also specific app option available
To enable assistant menu just go to
settings>>accessibility >>interaction and dexterity>>assistant menu>>enable and also click on it and enable>> assistant plus menu
what u wish is not practical, cos countless sreenshot will be captured whenever u touch that single BUTTON accidentally, that's why power button and lower volume has to be pressed to do that. well, try PALM SWIPE which is available for all samsung devices.
