Do not make a male to male 12VAC electric cord.
There are several very good reasons to avoid this plan, in order of increasing importance:
1. It's easy to overload the inverter. This would also apply to plugging the shore power cord into it, but this is by far the least important of the concerns. Be careful to turn off all the unwanted power users, like the fridge (on AC), the A/C, the converter, etc.
2. If you accidentally leave the inverter connected when you then plug into shore power or start your generator, bye bye inverter and possibly hello spark and light show.
3. The shore power cord is live when the inverter is on, and has exposed prongs. Touching them would be bad, potentially fatal.
4. Should the suicide cord become unplugged, it has a live end sitting on the floor waiting to be stepped on. This could be bad, potentially fatal.
4a. Should you unplug the inverter end but leave the wall end plugged in and connect to shore power, you have the same problem, but with a larger current source that would be more likely to additionally cause a fire as well as posing an electrocution hazard.
For safety, all AC electrical plugs and sockets are arranged so that the socket (with the enclosed contacts) is live and the plug (with exposed contacts) is dead. Please don't defeat this system.
