"Key to choose the 3rd level" enforces itself to use Right Alt key no matter what user wants

I prefer to use Alt + Tabs for Switching applications.
I prefer to use Super + Tabs for Switching Windows regardless of which workspace the app resides on.

But because of this, no matter how many times I disable it, or even change it with another value, but somehow it comes back to the “Right Alt” key! What’s going on over here? Isn’t it too weird?

This is creating a problem. I can’t switch applications with Alt + Tabs anymore. I have to redo everything (i.e Go to Tweaks > Additional Layout > Key to choose the 3rd level > disable Right Alt Key) again and again, which is very annoying.

What is 3rd level? And what it disturbing/altering my Right Alt Key normal behaviour?