You can already sort your photos by RAW and that's a super helpful feature. But if you shoot simultaneously in RAW and JPEG or edit your RAWs into multiple JPEG files, they will appear as 2+ different files by default. What I'd like to see is RAW+JPEG Stacking, where JPEGs are are associated with RAW files as a thumbnail, so that we don't have these duplicates when we open Photos.

Alternatively — and simpler to implement short-term — a JPEG file type filter could be added to the top of the Photos tab and the requested functionality would be half-way there.