If this is a feature of the home screen then it is something produced by the "launcher" app. The launcher is the app that produces the home screen and app drawer (these are not part of the operating system but a separate app). This means that whatever it is must be a feature of the launcher, and so must be controllable through the launcher's settings (which are probably separate from the system settings - I say "probably" because it's possible that Huawei have integrated them into the system settings, I don't have one of these devices to check). If you've not found specific launcher settings, try pinching in from the home screen, or a long press on and empty spot on the home screen - these are common places to find launcher options.
If it appears on every home page I'm guessing that means it is in the "dock" (row of icons at the bottom). Have you tried a long press and hold on this icon then seeing whether you can drag it away (or whether you get a pop-up menu)?
If all else fails, you could always install a different launcher. This would get rid of the button because it would replace your home pages entirely (so you'd have to set them up again). This is fine if you wanted to use a different launcher anyway, but a bit crude if you just want to remove one button from it. Another "heavy handed" solution would be to locate the launcher app in the list of apps and clear its data, but that would also undo all of your setting up.
