YouTube supports interactive-transcripts, using both machine-generated and user-uploaded transcripts. This is very useful for hearings, lectures, speeches, and educational videos where a visitor might want to read along or jump around. For example in this video:
https://www.youtube.com/watch?v=IY3U2GXhz44
The visitor can click on "...More" and then "Transcript" to view the interactive-transcript.
How does a video owner make that hidden feature automatically open for visitors? I cannot find any documented method for doing that through the API for either embed or linked videos. Is there an undocumented method in the API, or a URL parameter like "&action-panel-transcript=true" that works the way I'd expect it to?