While you can definitely bring in video captured with your iPhone 11, you cannot use it as the webcam during the screen recording. That is, you can record your screen, and separately record a video with your iPhone, but you'll have to sync them up in Camtasia after you're done.
Thanks Paul. Understand. Can you recommend a webcam that does work? I have a good Canon camera but it is not where I am and will take a week to get to me. If I have a recommendation of something I can buy at BestBuy, I can order online and do a curbside pickup at the local store.