Not sure you looked around on the The Behavior Panel’s YouTube channel, but they did some pre-debate videos regarding President Trump’s and Biden’s base body language to give people an idea of what to watch for the debate.
Part 1 debate profiling tips: https://www.youtube.com/watch?v=UdYoQPlW_LA
Part 2 debate profiling tips: https://www.youtube.com/watch?v=N5iEQ2_c-Fw
Part 3 debate profiling tips: https://www.youtube.com/watch?v=nZLWCY2IxFM
Then they also made a video about debate stress body language on both of them: https://www.youtube.com/watch?v=wQfNxg7PJHM