Please have a look at this: GitHub - educational-technology-collective/etc-jupyterlab-cell-iterate-run
It isn’t a pip package, but you can install it into your current JL 3.0 instance by following these instructions: Extension Developer Guide — JupyterLab 3.0.14 documentation
Or, do a development install as shown in the README.
Please have a look here at how to put together extensions: GitHub - jupyterlab/extension-examples: JupyterLab Extensions by Examples