Created attachment 154550 [details]
Screenshot with both displays

SUMMARY
With a FullHD Laptop display and 2K external display, disabling the laptop display (closing the laptop lid) breaks icon and window button scaling on the remaining display. It doesn't matter if the laptop display or external display is configured as primary.

STEPS TO REPRODUCE
1. Obtain laptop with FullHD screen and 2K external monitor.
2. Start a Wayland session with both displays.
3. Close laptop lid

OBSERVED RESULT
Window icon (upper left corner of the window) as well as the window minimize, maximize and close buttons scale breaks and their size doubles.

EXPECTED RESULT
Window icon and button scale is not affected by disabling the laptop display

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Linux 6.1
KDE Plasma Version: 5.26.4
KDE Frameworks Version: 5.100
Qt Version: 5.15.6

ADDITIONAL INFORMATION
See screenshots attached