Widget state is accumulating, even after clearing

[dsblank]

We have a notebook here that grew to 22 MB:

https://github.com/Calysto/conx-notebooks/blob/master/MNIST.ipynb

We would occasionally Clear Notebook Widget State, save the notebook, and verify that the size was small. Then, after a Save Notebook Widget State it would again be 22MB.

Our workaround was to actually close the notebook, run it again, and save the widget state from the freshly opened and run notebook.

[jasongrout]

See also #1866, where we discuss the convoluted procedure to actually get rid of old state, and a proposal for simplifying the menu options to make this simpler.

[jasongrout]

Discussion is happening on #1866 and #2012.

[dsblank]

Is this still an issue?

[jasongrout]

Yes, we had lots of discussion and experiments about the workflow around removing state, but I don't think anything really made it finally into the codebase.