xyflow

React Flow | Svelte Flow - Powerful open source libraries for building node-based UIs with React (https://reactflow.dev) or Svelte (https://svelteflow.dev). Ready out-of-the-box and infinitely customizable. Maintained by xyflow on GitHub, where it has earned 37,910 stars from the community.

It's actively developed around flowchart, graph, typescript-library, and is a solid reference for anyone building with these tools.