How to install it

KWin needs custom KWindowSystem, so build and install it first

cd kwindowsystem
makepkg -i

Once you've done that, build and install KWin. Keep in mind that compiling KWin may take some time if your computer is not very powerful

cd kwin
makepkg -i

Restart kwin_x11 by running kwin_x11 --replace command in KRunner.