I think it holds the rear camper support bar up when you don't have the camper top vinyl installed. These open ended threads with no clear answer are bugging me, lol. I need closure.
Not sure if you addressed this yet, but once you disconnect all of the water lines, it pulls right out. it is under the front v-berth cushion. Your leak is probably coming from the water outlet on the bottom right. Bouncing around tends to stress the outlet connection.