I’d like to develop an extension that works with VODs to set the playhead to time T (aka, seek) and also reads what time the playhead is at currently. I have not seen that this is possible in the documentation. Does anyone have experience with this? Thanks!
You can do stuff like that via the embed scripts for embedding codes on another site
Extensions exist in a channels panels below a stream or over a live stream. They do not exist not can interact with not a live stream
You cannot do what you describe as a on platform twitch extension