While doing research on some other things related to graphs. I blasted through my bookmarks from the past to recall JointJS and then dived in a bit to see how it works.
Just wanted to note that there’s a graph JavaScript library used in JointJS (MPL license) called Graphlib (MIT licensed) that provides data structures for undirected and directed multi-graphs along with algorithms that can be used with them.
Depending on what we ultimately go with for a design system itself for visualizing history, perhaps either library could be used.