"Quick lauch" "Graphical component" of "plasma-desktop" records neither position nor size

[[e-mail]]

Context :
  Hw = Laptop PC MSI GL72-6QF-813XFR, with a 256 Go SSD
  BIOS and Firmware up to date (March 11, 2018)
  OS : Kubuntu Bionic Beta 1, french configuration (on SSD)
  Installation : nominal (PPA : none beyond the nominal proposed)

Bug generation is trivial :
    install Kubuntu Bionic Beta 1,
    unlock graphical components
    command "Add a graphical component"
    select the "Quick launch" one
    fill the "Quick launch" area with some applications or shortcuts (example : 4 items)
    re-locate and re-size this "Quick launch" area
    lock (or not) graphical components
    restart your computer (or your session)

Test (wrong) result : the "quick launch" area doesn't take place as commanded (neither position nor size).

Nota : I found that no file is modified when I resize or move a "quick lauch" area (by "ls -Rla ~/.*")

Help for bug correction (may be) :
The "ItemsGeometries" structure of "plasma-org.kde.plasma.desktop-appletsrc" in "~/.config" is not modified when the "Quick Launch" area is moved or resized, and is modified at session startup.

[[e-mail] (jph-lebrat)]

This bug reporting is inappropriate within "Rip" package, but it's so hard to find the true path to report such a bug (I read many pages and tried many ways, but none provides me the solution). Could somebody help me ?