Unable to immediately continue Jupyer Notebook after closing then reopening the project
If you


run a jupyter server
open a new notebook with one cell: x=1
close the notebook
re-open the notebook
add another cell under the 1st: x+1


it would output 2, showing that the variable you had set is still in memory in the kernel

But, if you completely shutdown the jupyter server, or if you shutdown the kernel of your notebook, then you'll need to re-run the whole thing.

EDIT: JupyterLab is now in Beta and worth trying out as recommended here