I connected a second monitor to may laptop but set the laptop screen as primary screen. When I start a new program (from krunner, application launcher, terminal, dolphin) it will always be placed on the secondary screen. IMHO all windows should be started on the primary screen.
xwininfo and xprop of affected window please
I'm sorry, I can't reproduce it any more. Now it follows the focus (if a window of screen 2 is activated, new windows will open on screen 2, ...). This seems to work as intended. I'll reopen this issue if I experience it again.