Selenium -> Bleach

Can toning first in Se, washing, and then subsequently bleaching back be used as a utility process to pin down blacks and low-mids but shift the rest of the print upwards without the shadows being affected?

As fred picker would say, 'try it'.

Yes, limited time in a Selenium toner bath hits the dark areas first, and converts the silver to non bleachable form.

Subsequent bleaching will have the greatest effect on the highlights, and limited bleaching in midtones.

If subsequent tonng in other than Se is done the effect can be a very intersting, or strange, duo-tone effect, depending on the photo's image content.

Wash well in between or the high values may possibly shift color with some papers.......

Yes, and I prefer this order. Bleach works all densities simultaneously, even though it is initially not noticed in the shadows. Going with selenium first really locks in the blacks . . .better have a wet untoned print right next to it for reference, though. Some papers grab selenium pretty fast. I start with a cold solution of 1+9 and go from there.

Barry Thornton, Edge of Darkness, Chapter 14, this is exactly his thinking. I also pre-bleach a dry print, per A. Adams, The Print, Chapter 6, to clear the whites.