For ergonomics, the plugin should be able to spot cuts in the video so you can easily select the correct frames.

This shouldn’t even be too hard, I doubt YouTube is completely rerendering every video with ads, they’d just insert the ad in before an I frame in the video. So each ad will start with an I frame, and the video will resume on an I frame, meaning just let the user select all the I frames, no fancy cut detection algorithm is needed.

I have no idea how to do this from JS though.

Also I mean video I frames, not HTML iframes.