I had the magnify button enabled for use with a game on my N6P and when I restored my settings on my new OP6, that carried over. Problem is, it doesn't work properly so I'd like to disable it.

Unfortunately, that doesn't seem to be an option. Although I see "magnify with button" under accessibility settings, the setting isn't there when I drill down into it, only "triple tap to magnify". I tried enabling that, in hopes it'd overwrite the icon, but it doesn't. You can see the icon here, on the bottom right.

I keep on hitting it accidentally and it's driving me crazy. Is there some app setting I can clear to reset it, or am I SOL until OP fixes it?

Related PSA for people migrating who might have the magnification icon on - disable it before shutting your old phone down and migrating over and save yourself the hassle I've run into.