Temporarily block Internet access for the whole system?

Is there any way, within Comodo Firewall, to quickly disable/enable the Internet (or network) connection of the whole system?
Something like physically disconnecting/reconnecting the Ethernet cable?

I know that Internet can be blocked on a single program basis, but I’m looking for a quick and easy (and safe) way to totally disconnect the system when I want to work offline and I’m wondering whether Comodo FW can be an option.

Thanks for your useful help.
I noticed that when right-clicking on the “Stop Network Activity” item I get a context menu saying “Add to application bar” which, once selected, turns to “Remove from application bar”.
What is that option meant to do?
As I can’t notice anything happening in my system (Win10 64), shall I deduce there’s something wrong with my environment?

It adds the task to the task bar of CIS which can be found on the main screen or widget.