Bug 459357

SUMMARY
After system update, switching virtual desktops became very slow.
Possibility to change it's speed has disappeared.
Some windows are being improperly displayed during switching between virtual desktops.

(Please see attached video link)

STEPS TO REPRODUCE
1. (Optional step) run Conky or other window overlay app,
2. Turn on the "Slide desktops when switching virtual desktops" animation option,
3. Try to switch virtual desktops.

OBSERVED RESULT
Animation is very slow. (Much slower than in previous KDE version.)
There is no option to change it's speed. 
Overlay windows such as Conky are being displayed on top of other windows during animation.

EXPECTED RESULT
Slide animation should have option to customize it's duration.
Rendering overlay windows should be the same during animation as during normal operation.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Manjaro KDE
KDE Plasma Version: 5.25.5
KDE Frameworks Version: 5.97.0
Qt Version: 5.15.5

ADDITIONAL INFORMATION
Video link:
https://www.youtube.com/watch?v=9qMFfbyl5L8