I thought I tried the panel spacer, and maybe it more or less did the job, acting like some aggressively spring-loaded gadget but also squashing other applets, but none of this is an improvement over the control of panel applets and icons in KDE 3.5. One would have thought that the usability experts would have stumbled across something nicer than the "it's stuck to the mouse, how do I get it off?" paradigm for configuring the panel arrangement.
I also don't think it helps that the applet chooser (or whatever it is called) is a long thin window that sits above the panel and has to be scrolled large distances horizontally. It's not as if the remaining 90% of the screen is unavailable to show the available applets because we have to keep an eye on the progress of our city/civilisation/spaceships. Also the choice of horizontal scrolling must surely be some kind of joke in the age of the scroll wheel.
And let us not dwell of the function of the scroll wheel as a workspace switcher when the mouse points at the desktop background. A neat hack for some, but when the scroll area of a trackpad maps to the same function, it's like some kind of cruel experiment for many groups of users. "Why does the screen flicker and I sometimes lose all the windows?" Because someone thought it necessary to be able to "scroll" through 50 workspaces in one finger movement.