Which packages set up their own /etc/rc?.d/[SK]nn<package> initscripts?
 

Do packages in slackware install individual initscripts in /etc/rc.d/rc?.d directories, by that I mean the S??name and K??name startup and shutdown scripts.

I loaded up a plain-vanilla slackware64 15. Looking at it I see that all the installed packages' initscripts are hooked into the all-encompassing rc.[SM] script. rc.sysvinit doesn't really have anything to do.

I'm working with some tools that fiddle with sysvinit scripts, and I'd like to throw some real world situations at it, instead of creating my own stubs in rc?.d, that don't start and stop anything.

slackpkg file-search doesn't seem to return anything for me, but maybe I'm using it wrong...

No, but some third party applications may have installed initscripts there.