iOS shipped first; macOS followed through Mac Catalyst. The Apple lineup the company supported was iOS and macOS as two separate tracks, and iPad was not on the radar at the time. I was on the macOS team — Catalyst-based macOS work was the part of my role on this product.
The application is written in Swift with UIKit and RxSwift, and the workspace was organized as a single Xcode workspace holding multiple app projects, with networking, extensions, and other shared concerns lifted out into Xcode Frameworks. That layout shaped how I think about multi-app suites in general.
My macOS work covered the preferences window in all its tabs — general, security, notifications, chat, profile, version — the lock screen, the vertical tab bar, tray behavior, and desktop-specific app lifecycle behavior, down to the small helper application that launches Kakao Work when a Mac signs in.
I learned how to organize shared code across several apps and later used that experience when designing the SPM package layout at Certilife. This was also my first macOS development role.