I would love to see a way for notebooks to include other notebooks. By include I mean literally running the other one as if it was part of the current one: the same kernel, the same namespace.

In my, but I believe many other people's, use case the notebook often serves to keep well typeset (LaTeX) formulas next to their Python implementation and visualization. Now, I often want to run this on multiple sets of input parameters, keeping each set as a separate notebook for further tweaking. This means duplicating the formulas code between multiple notebooks, what further implies a lot of manual and error prone work with keeping them in sync. The other option - making them actual modules kept in plain .py is also not good, as I lose the well typeset formulas next to code niceness of notebooks.

Bonus points if print view would actually show the cells of the included notebooks.