I'm honestly tired of searching for programs that could download videos from YouTube.
You always expect that the free version of such a program will have the ability to demonstratively download a file. But no. And how then to buy a product in which you are not sure that it will work as it should?
Well, at least I was able to understand the chapters on YouTube. Mainly thanks to this article https://gyre.pro/blog/youtube-video-chapters-how-to-add-them-why-they-increase-views which means everything is better than I could have thought.