Just wanted to let you know that it is now possible to jump to the definition of a variable in JupyterLab with an extension of mine: jupyterlab-go-to-definition. It may not be as powerful as the PyCharm’s one, but should be good enough for a start.
Sorry for reviving an old thread, it’s just that I’ve seen this topic a while ago now, and it convinced me that working on this extension would be useful for others. Hope this will work for you too.