I used a six-pole, three-position, center off rotary switch rated at 60 amps for a manual transfer switch.
The converter was wired to the same CB that powered the non-GFCI circuits so I moved it to its own breaker.
Two poles of the switch direct the hot and neutral of the inverter and shore power to the main breaker. The other four poles interrupt power downstream of CBs for the AC, WH, converter and the outlet for the fridge when the inverter position is selected.
When the switch is in the inverter position the MW circuit, GFCI circuits and non-GFCI circuits are all powered. The converter is automatically turned off and the things I can't or don't wish to power from the inverter can't be accidentally turned on.
The transfer switch is usually left in the inverter position since we rarely use FHU. The only thing we have to remember to do is turn on the inverter remote switch.
So far it has been idiot proof.