How do you modularize your Xcode projects?

Hey there, I am currently trying to get started with macOS development in Swift. I'm not new to Swift as I spent quite some time exploring iOS development; however, over the last few months, I was mainly working on an API and therefore haven't had any exposure to Xcode or Swift. It feels like I'm starting from scratch again.

Anyways; when working on my Node.js projects, I simply used git submodules to share code between different projects, which worked out just fine for my purposes. However, I read something about submodules being way more complex than eventual alternatives when working on a macOS project.

Therefore my question: how do you avoid rewriting code over and over again for every project? How do you share logic between your apps?