How to use debugger in JupyterLab

  1. Is there a way to add a new watch in the debugger?

like a breakpoint on watched expression? Sorry I did not get the question.

  1. Is there a way to use a view (e.g. scientific view) to easily watch complex object such as dataframes?

There will be in 4.0! https://github.com/jupyterlab/jupyterlab/pull/10299 was already merged and there is an ongoing work on Update variable renderer panels by fcollonval · Pull Request #11171 · jupyterlab/jupyterlab · GitHub.