Can't use extension in jupyter 'jupyter_contrib_nbextensions'

I am new to Jupyter notebooks and I wanted to have a tool for automatic autocompletion of the code and to have a variable explorer like in Spyder. I found 2 Stackoverflow pages (Autocompletion in Juypter, Variable Explorer in Jupyter) recommending to use the jupyter_contrib_nbextensions.

I did exactly what is written in those posts for Anaconda and I could install the 'jupyter_contrib_nbextensions'. I also installed the 'hinterland' and 'varInspector' extension and I can see the extensions in Jupyter notebooks and activated them (see screenshot). However, I just can't use it. Somehow nothing has changed when I code in Pupyter. Do I have to activate somehting further?

One problem that comes up during activation using the terminal of Anaconda is that I get an message that I do not understand. You can see that in the screenshot. Maybe this has something to do with my difficulties using those extension (but maybe not) .

Does anyone have an idea what I have to do in order to use those extensions? I'd appreciate every comment and would be quite thankful for your help.

Do I have to somehow activate it at another position (e.g. directly in the notebook)? Any ideas what the warnings/error messages in the cmd mean?

Reminder: As I have not received any comments or answers to my question, I would like to remind you on this question. I tried a lot without success with is why I'll highly appreciate any idea for tackling the problem from you.

Does nobody have an idea what I can do in order to tackle the problem? I'd highly appreciate every comment, even if it is only worth a try.

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