If you ever feel constrained by the tree data structure, you might like Semantic Synchrony, which hosts a graph, editable from Emacs: https://github.com/synchr

If you ever feel constrained by the tree data structure, you might like Semantic Synchrony, which hosts a graph, editable from Emacs: https://github.com/synchrony/smsn https://github.com/synchrony/smsn (I'm a minor author of the project. It's kind of in a state of disrepair; Josh and I are both working on replacements for it. But it works!)