The Smart Vent Identification Mode setting is located in Home Settings->Flair Devices. This setting will turn on the light bar on Smart Vents when enabled. The light bar will display the unique pattern that identifies a Smart Vent.
It will take a minute or so for the vent light bar to turn on/off after enabling/disabling this mode.
After 30 minutes this mode will be automatically disabled. There is a live countdown in the UI of this timeout.