How to disable automatic spell checking?

I'm a Mac user. I have a different issue with spell check than most of the above comments, unrelated to underlines. To be honest, underlines are the least of my concerns.

Anything I enter in 1Password is likely information I want ultimate security with. The idea that I might type very sensitive information into a note in 1Password, and that information is being handed off to a system spell checker, really freaks me out. I can't figure out why a spell checker in a password manager seemed like a good trade-off in terms of highest possible security vs. convenience.

I also don't understand why this issue has been discussed for years now yet there's no action being taken. I really want to know my password manager is as secure as it can possibly be, misspelled words are really not something that's important in a password manager.

All said, is it possible to give an argument why having 1password entries routed through a spell checker (in my case, I think it's the Mac system's spell checker), doesn't needlessly add a potential attack surface?