switch between shell and anaconda in serial console

as are indicated at the bottom of the console, there are 5 windows in anaconda, you can toggle any of them by press:

<Ctrl> + <b> + <window number>

in a tmux style.

refer to:
https://docs.centos.org/en-US/centos/install-guide/Trouble-x86/
https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/installation_guide/sect-consoles-logs-during-installation-x86