Check Spelling While Typing in macOS app
macOS has this built-in feature to check for spelling and autocorrection globally, no matter what the context or app is. I highly doubt if it's available in Zotero, and I'm not sure how challenging it is for maintenance and debugging. But, it would be great to bring it to the Mac app version so that it creates a consistent experience for users across different platforms (i.e., macOS, iOS, and iPadOS). More specifically, and just a FYI, I think it makes people's lives easier when they're taking notes on highlights in the annotation sidebar. Thanks a lot for all the hard work and the contribution to society!
Unfortunately, I think it would be technically infeasible to support macOS autocorrect — Zotero is built on the Firefox platform, and Firefox doesn't support it, either.