Feature request: sandwich mode, but by file

For a particular application I'm working with, when certain optimizations are turned on, they affect everything in a specific file. I'm trying to find which files I should turn those optimizations on for (there are tradeoffs getting in the way of doing it for all files).

I'd love a mode similar to sandwich mode, but grouping on files instead of symbols names.

(Thanks for this project btw, I've been raving about it to all my coworkers 🙏)