Similar to quick tiling to left / right, but places window in the middle of screen, width is changed to half of screen width if it was less.

installation:
1. install with systemsettings or download archive, unpack it and execute in created directory as regular user:
$ plasmapkg --type kwinscript -i .
2. create custom shortcut with this command:
qdbus org.kde.KWin /Scripting loadScript ~/.local/share/kwin/scripts/quickTileToCenter/contents/code/main.js; qdbus org.kde.KWin /Scripting start
Path to main.js can differ on your system, check it!

When you use shortcut, current active window will be tiled to center of screen.