Since a few days I've been looking for a KDE replacement of RocketDock, which is basically a quicklaunch bar at the top of the screen.
Today I came up with a nice solution, which isnt a perfect replacement, but enough for what I wanted:
First, right click on your desktop, preferably in the top area, and select "add panel"->"Empty panel". You will see a new, empty bar at the top of your screen.
Now click "add widgets" and type "quicklaunch" into the search box. Drag the "quicklaunch" widget into the empty panel and add your desired applications.
It will look similar to this:
Now I do some extra configuration to make the panel occupy a minimum space on my desktop.
First it would be good to have it align in the center of the screen, because from center to top is shorter than from the center to the corner.
So, right-click the panel and then "Panel Settings". Click "More Settings" on the right and select "Center" and "Auto-hide".
Below the panel you can see 4 arrows which determine the minimum and maximum width of the panel. Drag the lower ones to make the panel so tight that it merely fits your quicklaunch widget. If you dragged too far, you can use the upper arrows to expand it again.
With the slider the center you can align the center of the panel. Now drag the "height button" a bit down to maximize the icon size.
If you like to, you can add additional widgets, for example a system monitor.
When you are finished, click "lock widgets" to hide the useless panel settings icon on the right.
Voila, here you got your centered, auto-hiding quick-launch bar!