Saturation actually comes from video processing, I think -- in analog color video (at least with NTSC signal) you can, with a suitable "box", alter the amplitude ratio of the signals for brightness (the one that's compatible with old B&W sets) and color (the one that overlays color on the brightness signal), so as to change the resulting picture pretty continuously from completely monochrome (gray scale) to garishly oversaturated.

The nearest I can think of that would work in a wet darkroom would be, starting from a transparency via internegative, to overexpose the negative and then compensate exposure in the print; both will tend to produce extra dye compared to normal exposures and will thus tend to slightly increase saturation -- but it's not a commonly applied control, because it requires starting from scratch with an internegative (or, if your original is a negative, making an interpositive and *then* an internegative).

Overall, aside from changing actual products (i.e. switching from Portra 160NC to Portra 160VC), the only way I know of to affect saturation of color negative film is to increase or decrease exposure -- which has other effects besides altering saturations.