This info may not have any relevance to this thread but I have already reported the config option on SystemSettings > Common
> Appearance and Behavior > Application Appearance > Icons > Advanced > Panel ... which had been broken throughout the 4.x.x SC. One of the KDE devs suggested that the config option be killed.
Hmm... Funny then

That is the reason why any number of tweaks by me on that option had no effect whatsoever!
Thanks Archie. I will give up on that.
[rant]
Watching a few bug reports on KDE, watching what every one is doing to OSes/DEs in general right from mobile to desktop (Mac, Win 8, Gnome and gradually even KDE) saddens me a lot. It seems being straight jacketed is the way. Freedom / choice are to be disabled step by step.
Modus operandi:
- Take a feature filled software.
- Blame the devs for making it too complicated.
- Reduce features / customisability in the name of streamlining.
- Drop an existing feature if it does not work properly instead of fixing it.
- Progressively end up with only a blank window

[/rant]