Hi,
I added an auxiliary shore power cord intended to run just the converter.
I powered the RV from the inverter. I kept the batteries up by using a combination of solar and shore power.
The term used for doing this is "double conversion". I did it when mouchdocking with 15 amp shore power. It allowed me to run the RV as if it were on a 30 amp shore power.
If you do follow this path, be sure to have some spare fuses for the converter.
I can't see that a transfer switch would be particularly useful. It would need to be a "smart" programmable unit. Do you have a link to the video?
I've not done this since I got a hybrid inverter/charger with load support.