If you have two displays connected on your KDE system, you might notice sometimes that your programs open on the wrong display. (Yes, I mean you, Keepass.)
Here’s a quick fix to this problem:
$ kcmshell4 kwinrules
$ kcmshell5 kwinrules
Give this new rule a name in Description: box e.g. “On primary display”
Select Window types: Normal Window, Dialog Window and Utility Window.
Click Size & Position.
Select [x] Ignore requested geometry, select Apply Initially from the dropdown and select Yes.
Click OK and then OK again to close kcmshell5.
KDE 4: Go to
System Settings Workspace Appearance and Behavior Window Behavior Window Behavior Focus/Multiscreen behaviour/[x] Active screen follows mouse Advanced/Placement = Under Mouse
KDE 5: Go to
System Settings Workspace Window Management Window Behavior Focus/Multiscreen behaviour/[x] Active screen follows mouse Advanced/Window placement = Under Mouse