Oof
"Extract audio and video files from streaming HTML5 video. You can combine audio and video streams together with third-party plugins." ...body, if you're not gonna do the work properly, just don't do it...
If IDM can download audio and video together why can't you? smh

沒看到任何按鈕，另外高畫質只是噱頭，截圖都顯示不帶聲音，代表只能抓串流而沒有合併的功能

for the first video I tried, it offered 360p audio+video. But video 720p and 1080p were video-only. You have to turn showing audio-only and video-only in settings to see them. One would have to combine audio and video outside of this addon after download. At least that's how it appeared to me.

Latest version not work with old design youtube. I prefer better tutorial (user friendly solution) for integrating audio downloader.

For some reason it stopped working with youtube?