Coppice is an app that allows you to lay out your thoughts and ideas on a canvas and view the connections between them. Using hyperlinks, you can create interactive mind maps — perfect for brainstorming that new project or your next D&D session.
Coppice was built by Martin Pilkington of M Cubed Software, who is sadly no longer with us, who generously decided that it should be provided open-source as example code of a modern, complex AppKit-based Mac app, built in Swift and relying on Xcode's Testing workflows. The repository is preserved here in full, rewound to the latest major version's working state, v2023.1. It supports macOS 12 and newer.