On my Janome 4030/or 30/40 the spot is not visible. (please excuse, I readily flip numbers) You must take off the "arm section" that can hold supplies. The switch is in the rear of the machine itself. You need to peer around to find it and push to move it. Sure enough, the feed dogs go down. I cannot really do free motion quilting, but I did try.
Hope this can help with your machine. If it does not go in and ask you sales/repair person. Mine showed me.