I’ve just switched from KDE to I3 just out of curiosity. But my key shortcuts/bindings don’t work at all. The default mod key is set to super which I’m assuming is the windows key but it doesn’t work. I’ve also tried alt and control too but no response at all. I can’t open the terminal so I can’t open any programs from there either.
Depending how you installed i3wm, the shortcuts you had set in KDE Plasma will not work, because i3wm is using its own config.
Mod key will work only in combinations. This are the default Manjaro predefined key shortcuts
Default location of the file is /etc/i3/config
You can copy it to your home directory under ~/.i3/config and edit it to make it your own.
Most likely you will have to satisfy that curiosity by reading i3: i3 User’s Guide