vismm is a self-contained web browser app for concept mapping. Check out the help.html file. Try vismm now:
https://obermann.github.io/vismm/index.html
https://obermann.github.io/vismm/index-solarized-light.html
https://obermann.github.io/vismm/index-with-sample.html (to start with something)
I used vismm to create a HDMI CEC (Consumer Electronics Control) protocol concept map.
GraphViz file format support can be tested with a convoluted test file.
In style
subdirectories there are three examples of vismm style customization.
For vis.js specific styling see vis-network documentation
or better still consult vis-network version 8.3.3 documentation (https://github.com/visjs/vis-network/archive/refs/tags/v8.3.3.zip).
JavaScript files are commented and more or less modular (e.g. input-output.js could be omitted and sample.js added for read-only demo).
Consult GraphViz documentation to style saved graphs or customize input-output.js.
https://github.com/obermann/PEG4DOT
https://dreampuf.github.io/GraphvizOnline/