Yes exactly, "riding the gain" with the modern possibilities of drawing envelopes visually.
Gates, Expanders, Compressor, ect do basically the same thing in an automated, often very predictive and wrong or at least compromised way. So, why not do it manually here and there?
I also find it useful in mastering applications. Of course, it makes sense to do whatever possible already in the mix. But (not limited) mixdowns often only have 2-3 really significant peaks. In my opinion, these are better tamed by hand, so that the final limiter works with a more consistent input (means less distortion and more control).
Also, I often receive horribly squashed, loop-oriented mixdowns lacking any kind of dynamic contrast. I found it useful to manually "turn" down some parts of the track to let the chorus better kick in (just an example). Of course, all parts will still peak around 0dB after the final limiting, but only the chorus will be squashed like crazy for a few seconds, the parts in-between will relax the ear until the next chorus.
It's just an idea, a proper mix will not ask for such a band-aid of course.