It's indeed a bit unclear what tab he refers to. I had first thought the dome toolbar of KStars, then figured out it might be in EKOS -> driver question, as you answered.
But I see he's using stellarmate, could also be the app?
I experienced the same behavior. As soon as I connect my Pegasus PowerBox (which has a temperature and a humidity sensor), I then have the 'Dome' tab visible in Ekos.