Most systems allow the user to choose whether to move the scrollbar to the position of the pointer or towards it by a fixed amount when it is clicked.
Plasma, however, only offers that setting for GTK apps. In Qt apps, the user is forced to use the default behaviour: Left click to move towards the pointer, middle click to move to the position of the pointer.
A simple setting for this would improve the usability of scroll bars a lot.
*** This bug has been marked as a duplicate of bug 379498 ***