Plasma 5.18 allows to be configured so that left clicking (not just middle clicking) scroll bars in Qt UIs instantly jumps to the position of the cursor (and keeps on dragging the scroll bar when keeping the button pressed).
This doesn't work with LibreOffice kde5 VCL (e.g. in Writer), as it doesn't seem to respect QStyle::SH_ScrollBar_LeftClickAbsolutePosition.
It should do that so that it behaves like other Qt UIs.
Reported coming from here:
Michael: thought you might be interested in this one since it's KDE specific.
As far as I know, LibreOffice does not use a native QScrollBar (and most of the other native Qt widgets), but rather paints a scrollbar that is supposed to look like one, which may be the reason that it does not work "out of the box".
If somebody wants to look into this: From a quick glance, the code for painting the widgets is in 'vcl/qt5/Qt5Graphics_Controls.cxx'; the handling might be somewhere there or elsewhere, maybe not even in qt5-/kf5-specific code.
FWIW, the "gen" VCL plugin behaves the same, while gtk3 (which *might* already use native gtk widgets due to Caolán's welding work, but I don't know) behaves as it should.
This won't work without using the new "weld" theming API.
*** This bug has been marked as a duplicate of bug 130857 ***