SUMMARY
I have many issues with my dual monitor setup. 
1. When secondary display is disabled my cursor border is broken within games.
2. Corruption within Spectacle app whe nI want to make screenshot
3. Display layout is not restored correctly when i want to enable second monitor back.

STEPS TO REPRODUCE
1. Connect two monitors (full hd and 4k displays)
2. enable both displays with 4K being the primary one
2. Disable non primary display within plasma settings

OBSERVED RESULT
After I disable my secondary display I observe strange behavior. For example when I want to make area screenshot within Spectacle app I have corrupted display (video included). The resulting screenshot will not be correct.

Second, when I play proton games I observe my cursor has incorrect border. I cant move around my whole display but only within selected area. This does not happen when I unplug my secondary display.

Third, sometimes my display layout is not restored correctly. When I enable my secondary monitor, the layout is not the layout I used previously.

The only workaround is to disconnect my disabled secondary display or change scaling options.

EXPECTED RESULT
Monitor layout should be restored when I disable and enable monitor. Spectacle should not be corrupted and my games should not have weird border issue.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Fedora KDE 43
KDE Plasma Version: 6.5.1
KDE Frameworks Version: 6.19
Qt Version: 6.10

ADDITIONAL INFORMATION
I noticed this happened since KDE 6.2 or 6.3 (the version in which display settings layout changed). This behavior is the same in newest KDE version 6.5.1