Crossover mixer

This would be a “mode” or “variant”, like the splitter crossover variant, but on the mixer. That is, at the mix point, it would discard everything above frequency X on channel A, and discard everything below on channel B, then mix what remains to produce the full-range signal.

For example say I like the high-end of amp A, but the low end of amp B. This would give me the best of both worlds, and would open up a lot of tone-shaping options.

It can’t be done with a crossover splitter, since effects applied after the split tend to “escape” the crossover bands. That is, a distortion pedal—even though the incoming signal only contains 800Hz and below—will add coloration above 800Hz to the outgoing signal. The frequency-selection needs to happen after all effects are applied, i.e. at the mixer.

You could try using the current crossover option and just add high and low pass filters at the end of each fork of the split.