I like Joplin App, but I think Notebooks is show more, and I will distraction when see it
I know can press F10 for hidden but if I want change different Notebooks, I need open again
So, why you don't think about selection notebooks like Onenote design
I don't like Onenote text editor more because it text block is more...
But I like the way Onenote design
It will be a great if they will added it.
I think the better option will be to make a notebooks with some quite of description about the notebook itself.
Like in Notion when you create a Note you can make it like folder, write the title, add text and after that creating a notes in that.
For me creating a notebook but without adding the description of what inside the notebook is hard to remember for what I created that notebook.