Html layout from ipynb file in Jupyter-lab with R kernel

I’m using Jupyter-lab with the R kernel, wich I find much more friendly than Rstudio, but I’m having trouble when it comes to export my ipynb file to a nice html document.

Here is what I have before and after exporting using “Export Notebook As” in the file menu :

I’m a beginner in Jupyter-lab and I’m looking for references to learn how to make a nice html document.

The default export output should not look like that. Is this possible that you have any custom nbconvert templates/extensions installed?

I don’t know how to see that ? (I’m quite new to Jupyter and I see I’ve got much to learn).

In fact that was from the computer at my office, but in my personal computer it looks right. I’m just failing to add a side floating TOC. Would you know a good ref about it ?