If you’re ok with debugging shaders themselves outside an engine, SHADERed does an excellent job cross-platform: https://shadered.org/blog
Don't see a OS X client and the web version seems quite buggy - a number of the ones I tried to open loaded infinitely (with errors in the console).
I'll give it a shot on Windows...
Edit: Yeah, this is certainly a step forward compared to what I've been doing.
Being able to choose a quad/triangle/pixel and step through breakpoints is fantastic.
Not the best interface / ux, but it's motivating.