I've just created a github repository with a MacOS utility application that I developed to allow me to add program icons from images. It is only available from github and as source code, it is not available on the App Store.

This was one of the first SwiftUI apps I wrote so the coding may be primitive, but it works for me.

Feel free to use the app if it helps you, but remember to respect the license of any images you use to create icons.

Any feedback is welcome.

https://github.com/microenh/IconsetCreator

Nice work!