It's a cap that you can unscrew on the top end of the blue hose shown in your picture. Supposedly the plastic fittings should be able to be tightened enough so that there won't be leaks. However that doesn't always work. You might want to try this before you start removing toilets. It won't hurt anything and it might save you a step. Good luck.
I have a 2006 Wildcat and it leaked the first time I took it out I took back about 4 times and decided to repair myself I replaced the flush Valve. I had to remove the Foam sealer around the hose and loosened the hose nut pulled hose down and removed the two Philip screws to replace the flush valve. After replacing it I resealed and have never had a problem since and that's been since 2006