Pluto is the best notebook system I've used, and development is very rapid so it's getting better all the time.
That aside, I still have not found my ideal notebook client.
I don't particularly like the "notebook" format anyway. I prefer having my code and output side-by-side. I want to be able to toggle among the "code | output" vertical split layout, code-only, and output-only, on a per-cell basis. I also want the split to be adjustable in each cell, so I can make the code take up 90% of the width or 10% of the width if I want it to. I of course want cells to be vertically collapsible. And I want an automatic table of contents in a sidebar "drawer". I want reactivity between cells. I want an extension ecosystem with things like a nice file picker and a built-in Git GUI. I want to connect to remote kernels (this is supposed to be possible with the Jupyter ecosystem but practically it's not well supported). And most of all, I don't want to run it in a damn Web browser!
And if the text editor box was also an embedded Neovim frontend, I wouldn't complain about that.