You are correct, there is a sequence that keeps the socket live (computer controlled) for your charging. I believe you need either a BMW charger or a CAN bus rated Optimate charger.
I suggest making life easier and get a pit tail and wire directly to your battery with a 15 amp fuse and have the working end dangle at the bottom edge of the seat. This can be used any time with no tricks. Also good for an air compressor or a heated item of clothing. The oem socket is only 5 amps and will not run anything of use. Or better yet, purchase a BMW type socket and install it directly to your battery or a fuse block, using that 15 amp circuit demand. Do a search for Fuse blocks if that interests you.
Otherwise: first turn the key on to the bike, then you plug the charger into the accessory socket, then you plug the charger into the wall for power, then you turn the key off.
Mount Vernon, WA.
tire guy, I'll mount your tires.