How to increase contrast of scrollbar

[José Matos]

On Sun, 2023-09-03 at 23:36 +0100, Paul Stansell wrote:
> I'm using the following:
> - Global Theme: Breeze Twilight
> - Application Style: Fusion
> - Plasma Style: Breeze Dark
> - Colours: Breeze Light
> - Window Decorations: Plastik
> 
> KDE's program okular has the same invisible scroll bar as LyX.

As far as I understand the culprit here is the Application Style, what
happens if you change that to, say, "Breeze Dark"?

Regards,
-- 
José Abílio