It's certainly nothing that should you should be worried about and I think you are over complicating it! It's simply advisable to connect the negative charger lead to an earth point away from the battery if possible, rather than directly onto the negative battery post - that's all there is to it! I have used a smart charger on my Omegas for many years with no problems, usually when not being used for a few weeks; the only time I disconnect the negative terminal is when they have been off the road for longer periods such as the last lockdown.
As for the radio pass - with the NCDC 2013 or 2015 in the Elite with the original radio, then you don't need the code/ pass if you disconnect the battery. With non Elite models, if you don't have the pass, you can purchase a simple memory saver device for little money to retain the radio code whilst changing or disconnecting the battery.
They use the OBD socket (some use the cigarette lighter but I prefer the OBD type) and require an external 12v power source. I use an old 12v house alarm battery which is a convenient size for this task.
It's certainly not a dark art or complicated....