I can't see it on my map either.
I have the David Baines map (is this the one you have?)
Apparently it is towards the west end of floor 6.
I was planning to just walk right along 6 until I came across it.
Last time I did walk along for a few chambers. One chamber has a roof collapse near the tunnel but it is passable. Had I known about the incline then I would have continued. There is an adit to the west which has a crawl them needs an abseil. Not sure if this connects to the incline chamber. Then another adit further up which is blind and maybe in water.
Need another explore. 😉
May the fleas of a thousand camels infest the crotch of the person who
screws up your day and may their arms be too short to scratch.