Experimenting with a revised graphviz-viewer. Based on hpcc-systems/hpcc-js-wasm. UPDATE: Paul has updated the graphviz plugin to use this library. PR #10 
hpcc-systems/hpcc-js-wasm
https://wiki.dbbs.co/assets/graphviz-viewer/index.html
Demo doesn't fit well in this frame. Pan around or look in another tab: demo
HEIGHT 305
graphviz-viewer
For some reason the .wasm files have to be at the same directory level as graphviz-viewer.js, so I just put everything there for now.
Created this roughly as follows:
npm install --save @hpcc-js/wasm find node_modules/@hpcc-js/wasm/dist -type f \ | xargs -I % cp % .