Add a water hose, and pressure regulator so you don't over pressurize the piping and water heater. This is the one I use. https://www.amazon.com/Renator-M11-0...8385202&sr=8-5
Potable water hose if you intend to drink it, or just 'a hose' if you don't. Canvas hoses are especially nice when space is tight, like in a Class B.
I also carry a 50A to 30A dog bone, plus a 15A to 30A. The 50A is because it's all too common for the 30A receptacle in a park to be sloppy loose or burned, with a 50A receptacle that's still sound, and the 15A so you can plug in at home or a friend's house.
I carry a 25 ft 30A extension ford, but I've only needed it at my son's house so far. But it takes little space, so I carry it always.
Also get a windshield and door window cover. Or a curtain you can pull across, though the windshield cover is less obtrusive. I have the Sprinter version of this one from Adco, but there are others. https://www.rvcovers.com/products/do...ndshield-cover
Get what you need to winterize the water system, on the road, if intending to ever be in cold weather. And learn how to do it while it's still warm out, at home, so you know.
Try the galley - cooking, making coffee, and so on. Or just microwaving or camp stove. The time to find you need something is before you need it. Same with bedding, bathroom, and so on.
That's all I can think of off the top of my head.