@olivier92410 I think seaborn is in your “base” environment while KNIME uses the “py3_knime” environment. So you might want to activate the environment in your (base) prompt and install the seaborn package again.
conda activate py3_knime
conda install -c conda-forge seaborn
or in one step from the base prompt:
conda install -n py3_knime -c conda-forge seaborn
You might want to check out how to manage Python environments:
https://docs.conda.io/projects/conda/en/latest/user-guide/tasks/manage-environments.html
An even better way to handle things would be to have your packages in a YML file and change that and then order conda to update your environment once you add a package. Like in this example. Basic KNIME Python and then added some R packages (you could manage your own selection).
Maybe you read the somewhat lengthy text in the blue square here about KNIME and Python. Handling environments seems to be somewhat complicated at first. But once you grasp the 3-4 basic concepts it becomes a powerful tool - and KNIME would support you thru the environment propagation.