I discovered, after instantly blowing the 2A fuse in the “Auxiliary DC jack”, which we affectionately call the “cigarette lighter” jack, that 1) all the detailed information about the three fuse boxes and their fuses lies in the Owner’s Manual, (pages 7-33, 7-34 in my book) and not the Yamaha service manual, and 2) you’d better forget intuition, because when you assume the 2A fuse is in the location you’d believe, i.e. Fuse Box #2 and perhaps would be in location 6 or 8, since they are called “Auxiliary fuse” (1 and 2) – you would be wrong. The correct fuse is in Fuse box #3, and it was “Terminal fuse 1” location, (4). The label, inside the cap, showing the fuse ratings, was upside-down on my bike, leading to further confusion. The drawing in the Owner's manual is correct. There was a spare fuse in box #3.
By the way, the accessory I was trying to use was a small air compressor, not designed for a motorcycle, and apparently draws far more than 2 amperes.