how to save personal settings on desktop 11.1

I tried to set dual screen default in:

Personal Settings -> Display -> Position (Right of)

so that dual screen is utilized, but after next reboot the
settings is still the default and not my Position (Right of)

anyone knows how to do this?

You need to give a bit more information; what desktop version are you using? If you are using an early KDE4 version, you may simply need to upgrade.

The settings may well have been saved but not acted on which is what you want.