Start from the clock face and swipe right until you find the settings app - tap on it and scroll down to sleep mode - tap on that - you should be able to turn it on and also set an automatic schedule from here.
You could start a video stream, and press the power button briefly to turn off the screen or put the device. LEED3D You should be able to set up sleep mode from the settings app on the Charge 4. From code perpective you dont have to do anything more besides changing the app_default_sleep_mode in ARCH_EXT_SLEEP_ON in order for your device to be in extended sleep mode, please check if you change the sleep mode at all when the device operates (disable_sleep()). In the past this was possible with the Safari app. What is the developement board that you are using, a pro or a basic kit, if you are using a prokit you can use Smart Snippets and check if your device is sleeping between the connection or the advertising events.
