Update scaling without restart / relogin in KDE?

I am using Kubuntu 18.04.3 with KDE 5.12.9 on my Dell Precision 5530 which has a 4k screen. As I quite frequently connect a display (mostly just 1080p) and KDE does not yet support scaling per screen I need to change the scaling factor. Usually I set the laptop screen to 1080p with 1x scaling, but I always need to restart or relogin to apply the changes, which is quite tedious since all open thing get closes. As solution I tried to restart the plasmashell, but that does not work very well since the title bars does not get scaled properly after that. Is there an option that the system does it automatically, as it Gnome? Might it help to change SDDM to LightDM? Not sure if this actually makes more changes than just the loginscreen.

Thanks for help

You can try kquitapp5 plasmashell && kstart5 plasmashell </dev/null &>/dev/null & in a shell, but you'll still have to restart applications for the scaling to be applied