Is it at all possible for you to get the files of the world?
After multiple tests with various toggles on and off, it does do something. Turning it off stops commands from being able to be used in chat. It's basically the Activate Cheats toggle. You can still have Keep Inventory on whilst not having commands enabled, for example.
Have you taken a look at your controller settings within Minecraft?
You can turn down the sensitivity there, and also try remapping your controller buttons.
I believe this may just be an issue with your hardware, as I am able to use the Game Bar perfectly fine whilst in a world.
If you don't mind me asking, what components does your device have?
A few things:
Firstly, from the link you attached, I'm assuming you're playing on the Nintendo Switch version? When transferring your images or videos to other devices, you can't just provide the link as nobody else can access it, you need to actually download the media and upload it to your post.
Secondly, you can't just expect people to get back to you instantly, the team is constantly working on things. I'm sure they would see your post eventually, but keep in mind there are bugs from many years ago which are yet to be resolved!
Lastly, I personally don't see how this is an issue. You're not supposed to be able to get water in the Nether in regular survival, that's true, but if you're using structure blocks I assume you're in creative, a world with cheats enabled. You can get water in the Nether through the /fill command too, I believe. In the end, I personally don't see this as an issue at all, but if the devs choose to prevent this in the future, then I'm sure they will.
You have a Parrot on your shoulder.