Smart Home Control
To be able to control your smart home devices as a group rather than individually (e.g everything in a room), go to the Alexa app and select the Devices icon at the bottom of the screen. Next, either select an existing group or press the + sign.
Touch Control On Echo Show
When it's time to get some z's, you can use touch control on Echo Show devices to turn off the lights. First, swipe left from the far right hand side of the screen. Next, tap on the Smart Home icon, before turning off all your connected smart home devices without making a sound.