Ok,I understand the confusion.
12 volt systems are great, since they are DC you do not need to worry about something called phasing (just polarity) so you can parallel 2,3 or more sources of 12 volt
Battery (or Batteries) Shore power via the converter.. Solar.. Other all can be parallelled.. No rocker switch needed to switch from one to another they are all present all the time (provided you have the option and it is working)
In your case there are only two sources.. Battery (or batteries) and shore power
To switch ... UNPLUG from shore,, that's all you need do
The references to the rocker switch......
Elsewhere in your rig is a panel.. it has a bunch of LED lights and some switches.. likely one for the gray tank, one for the black and one that says BATTEREY or has a symbol of battery or lighening bolt
This is used to check the state of charge of the battery.. And .. is not all that reliable.. It has no effect on using the battery to power lights et-al. That is all automatic.