If you have a multi-monitor set-up and are wondering if it’s possible to control which screen is “primary” – where all your panels will end up in – yes, it is. That is, assuming your desktop environment asks X to decide which screen is “primary”. KDE Plasma does, and Gnome probably does too. As long as X is involved in the decision, it’s possible to use Xrandr to tell X which screen you want to be “primary”, by using the “–primary” option. For example, if I want my laptop LVDS screen to be my primary screen and get all my desktop panels, I’d run:
xrandr --output LVDS --primary
That was easy :) On a related note, some changes are forthcoming in KDE SC 4.5 in the way multi-monitor setups work. Take a look here for some details.