Swappiness can be thought of as the point that KDE neon decides to stop keeping files in RAM (fast memory) and start writing them to a swap file on the hard drive (slow memory).
Unfortunately the defaults for KDE neon treat it the same as the defaults for a server with swappiness set to 60. A better swappiness for the desktop/laptop is 10.
To edit the swappiness, open up Konsole and type,
sudo nano /etc/sysctl.conf
This will open the sysctl.conf file in nano. At the end of that file insert the line,
vm.swappiness = 10
And save it.