Actually I found “recovery” as a slider even for a Jpeg.
Yes but that is not the “Recover Highlights” Nik is talking about. That is only available for RAW pictures in the AI section (first icon beneath the histogram)
The recovery as you mentioned works as follows (Quote from the RawPower help function) this slider works like a “selective exposure”. Only the brightest pixels are affected, but unlike highlights, it adjust the brightness just like exposure. Sometimes you will get better results with Recovery and other times Highlights will work better.