There is a twin electrical outlet in a cabinet that was intended for the battery charger to plug in, and provides the internal connection to shore power. That was standard from factory. It's a Mastervolt 50-amp charger and that's a good unit (and pricey) I didn't want to replace but I also wanted an inverter for laptops/portable devices etc. that would feed the entire "grid" within the boat.

I bought a 400w pure sine inverter and mounted it next to the charger. The inverter has a direct DC connection to the same bus bar as the charger, so they are parallel. The inverter also has a 120VAC GFCI double outlet that connect to the boat's outlet with a short male-male cable, and the inverter also has a power on/off switch and I unplug both sides of the male-male as a precaution so that I never have live power on the unconnected male plug. I also installed a child-protection outlet cap in one plug position so only one device can be plugged in at a time, and next to it I put warning labels with bold-text all-caps advising NOT to plug both inverter and charger at the same time, and to unplug the inverter prior to plugging in shore power (also put tag on shore power cord to check inverter is unplugged, although it is supposedly protected with diodes). Bottom line is that regardless of all these warnings -- nobody in my family touches that arrangement but me so these warnings are for the next owner or anyone doing maintenance after I'm not in the picture (I do all my own maintenance). The outlet cap makes it fairly idiot-proof for me.

The inlet breaker panel (with GFCI) is remote from these devices, near the shore power external connection. It's the GFCI on the inverter output that trips unless I turn off this breaker, which actually is a good thing because it is yet another thing that will prevent me from accidentally connecting shore power while the inverter is still connected.

Hope that clarifies.