Currently chapters are supported in description. It will highlight currently played chapter and you can click to move to another one.
The main problem of this layout is you have to scroll to see and interact with chapters. You can’t see both at the same time, and it’s painful to go back and forth (even more when the description is long, as chapters are often at the end of it).
Piped has an amazing UI where chapters are directly visible if you watch the video without full screen. On desktop, it’s located at the right of the video and on mobile, just below the video.
The Piped UI basically looks like the YouTube chapters box.