Esc aborts and enter switches window. It is also possible to select window with the mouse. Configuration is installed to /etc/sway/config.d/swayswitch.conf
Two keybindings work by default, Mod4+f to toggle fullscreen mode, that is if you manage to bring up the switcher while in fullscreen mode you can display the
switcher window by exiting fullscreen mode. You can also exit switcher mode by pressing Mod4+q, this is usefull if you manage to get another window on to of