After I read this comment I downloaded Prusaslicer's latest version.
Wow. LIke S3D and unlike CURA, it starts up fast. It has advanced settings, allows setting various profile types and even directly (and simply) connects to Octoprint and Duet. I ran a quick Phil-A-Ment astronaut off on a custom printer profile and it was perfect. It will take getting used to a new layout, but it seems pretty intuitive. I will have to try the support settings, since that is what S3D is famous for. Scripting is easy too, so I will have to try its multi-filament settings on for size. And it is free and open-sourced.
Now to find its warts, there are always warts.