https://www.cnet.com/news/amazon-echo-alexa-in-app-smart-home-controls-just-got-a-makeover/

Tap one of the cards representing a group of lights and you'll see an expanded list of the devices in that group, with the option to toggle each individual device on or off. 

You can also tap little icons at the top that represent different categories of devices to see them all listed -- your Echo speakers, lights, plugs and so on. To add a new device or group to your setup, just tap the plus sign icon in the top corner.