In our contributing docs we have a section that describes how one could use a plotly.js bundle to test bundles from the last commits of pull requests or any plotly.js branch.
https://github.com/plotly/plotly.py/blob/master/contributing.md#circleci-release

This is generally fine; however, it has certain limitations.
For example the CircleCI keeps the artifatcs for just for few days (around two weeks).
So one may need to rerun the build process on CI after a while.
etc.

I suggest we add a script where one provides a link to a plotly.js commit similar to https://github.com/plotly/plotly.js#caf32e57cfdbd370076b926f84c114093f62f0b9 and then it updates the package file, install plotlyjs and rebuilt the bundles. Then copy the new file over.
Something like:

cd packages/javascript/jupyterlab-plotly/
npm install https://github.com/plotly/plotly.js#caf32e57cfdbd370076b926f84c114093f62f0b9
cd node_modules/plotly.js
npm install
npm run bundle
cp dist/plotly.min.js ../../../../../packages/python/plotly/plotly/package_data/plotly.min.js