Plasma 6 proposal: Unified panel spacing
Currently, spacing between applets is hardcoded, and some applets such as Task Manager and System Tray have individual options.
This can look bad when using a launcher next to a large spacing Task Manager:
I propose a single option for panel spacing, similar to what is already available in those applets, that can be changed to affect the entire panel, for the spacing between applets, and also read by applets for their internal spacing. Those applets can tune their own spacing and sizes to look good. We might consider three options such as "Small", "Normal" and "Large", and provide applets with a value for the spacing to use.
Outside of a panel, this value would just be the default normal size, or configurable by applets as it is now such that you can have a wide tray on the desktop if so desired.