question

We have a smart home Alexa skill with a custom lambda and our own back end server to control the IoT devices. The skill works fine with voice commands, and with our custom Android app. Now I want to also use the Alexa app to control the devices. But Alexa shows on screen buttons only if the device type (display categories) is set to LIGHT or SMARTPLUG. For other types like AIR_CONDITIONER, COFFEE_MAKER etc, only the relevant icon is displayed, and no on/off buttons are shown on the Alexa app. Can anyone point me to the relevant documentation on how to modify the behavior of the Alexa app?