Joseph Wright

What I guess I'm not seeing immediately is what the 'combining advantage' is. With `\qtyproduct` and even `\numproduct` there are some common elements that can get pulled out, e.g. exponent....

This is quite a niche requirement, hence it doesn't really belong in the quick start guide. I'm happy though to think about how to make it a little easier to...

I think related to https://github.com/josephwright/siunitx/issues/580. What I haven't really seen is a strong motivator - unlike `\num`/`\qty`, there's no real likelihood of wanting to combine an exponent, etc., so there's...

You don't say how you define `\molar`, but assuming `\DeclareSIUnit\molar{\mole\per\cubic\deci\metre}`, your output is exactly as expected. Units don't 'group': `\molar` is simply replaced by `\mole\per\cubic\deci\metre`, they the `\per` you've added...

At present no, I can log it as a feature request, but I'm worried it might be confusing overall.

This is something like an `table-align-uncertainty-decimal` option: doable but not currently implemented.

Free standing units have only ever been _intended_ to be used as single macros, so for your situation it was always expectedy you'd have ```latex \DeclareSIUnit{\kilometre}{\kilo\metre} ``` in your preamble...

Probably I should adjust the messaging here to be clearer

This sounds like a recipe for inconsistent appearance ... can you explain why it's needed?

In particular, I'd say the semantics of `\numlist` are that the entries are subject to the same formatting settings.