Sort by multiple keys

[JobLeonard]

This may be a bit of a weird request, but I have a specific need to mostly-sort by hue, then by diff (actual sorting wouldn't work since all hue/chroma/lightness are likely to be unique).

I guess it could be implemented by limiting the significant digits being compared (maybe even allowing for control of that), then using diff as a secondary key.

I'm going to look into the source code myself to see if I can come up with a functional snippet that does what I want, to give a better example :)