FOSS Linux published a tutorial about how to restart KDE Plasma Desktop without rebooting.
How to Restart KDE Plasma Desktop without Rebooting
Here's a guide on restarting your KDE Plasma 4 and KDE Plasma 5 Desktop without rebooting the whole PC. Once the Plasma shell is restarted, your PC runs faster.
How to Restart KDE Plasma Desktop without Rebooting | FOSS Linux