I would either unplug or turn off the circuit breaker at the shore pedistel
It's simply not worth the risk
There is always some one who says that is what it was designed for
Switching with power on,
The answer is no, that's not what it is for
In an RV it saves Changing from generator outlet to shore outlet when setting up camp, and it saves going out in bad weather and Changing back If there is a power failure
In home or commercial use it switches to backup generator AFTER utility power fails, Not while utility power is on and in use