I'm trying to find a way to set screen locking timeout programmatically. With the previous version of KDE, I could write to ~/.kde/share/config/kscreensaverrc and modify this line:

Timeout=<timeout-in-seconds>

and the setting would take effect immediately. With the current Plasma 5 Desktop, I can also add/modify these lines to ~/.config/kscreenlockerrc:

[Daemon]
Timeout=<timeout-in-minutes>

but the change won't actually take effect.