Default flick deceleration is far too high for touchscreens, can't be customized through platform theme

In https://codereview.qt-project.org/c/qt/qtbase/+/91242 FlickDeceleration was introduced as a value for Flickable that specifies how fast a flick decelerates. The speed was also changed from 1500 pixels / sec² to 5000 pixels / sec².

From my experience, this value is far too high and makes touchscreen scrolling painful, because there is almost no inertia when releasing from a flick.

I am aware that this can be changed through the flickDeceleration property of Flickable, but from working on KDE Plasma Mobile, we want to be able to change this globally. I might be misunderstanding the code, but from my understanding it cannot be changed through the platform theme at the moment, it fetches it from the platform which on X11/Wayland would always then fetch the default value.

I think the default should be restored, or at least, some way of changing it through the platform theme should be possible.