Do the store ranks (Service/Sales, which rise when characters act as store clerks) ever trigger anything?

As far as I know, it only affects the amount of sales and thus the money you make.

I may be wrong though.

Stuff sells for more/faster/etc.

Just to sum things up nicely in a single word: no.

Conveniently, this topic already vreated and i'll try and use it for another purpose^

Is there a way to expand workshop over 10lvl?
Or, maybe, recharge it with greater growth rate?
After 9/10 lvl it's pretty small and didn't expand space on the latest iterations.

It just seemed to me that i saw a screenshot with workshop being several times bigger, and can't see a possibility of making it.

Thanks.

If there is a way to expand it past lvl 10, I haven't found it (and I'm a Meister, currently on my 2nd NG+)

Nope, I believe lv10 is the max level 'm Magnus Rank, replayed the game a few couple of times already)