3-way Transfer Switch upgrade?

Hi Guys!
I am plugging my shore power into the ac outlet on a Goal Zero Lithium 3000 solar battery system (as if it's my shore power source) which sits just under my bed. And I want to see about a 3-way Transfer Switch upgrade for the present ac/dc distribution panel (also called power center).

That way I can avoid having the shore power cord run from the outside of the van into the van and Goal Zero pack.

Does anyone know if there is an upgrade option to this power center to make it from 2 way to 3 way? Thank you.

Manual or automatic?

Do you have a diagram of your current AC electrical system?

Something similar is on my list of upgrades too. I was initially thinking of just putting another 2-way switch inline to create the 3-way. It would be cool to just replace it with a 3-way. Following...

UPDATE- I'm waiting to hear back from AM Solar on the possibility that one of their techs can do this on the side.