When I delete a cell in a notebook, it is gone and I cannot get it back. It would be nice to be able to restore the cell.

I imagine the following: Immediately after hitting the "Delete" button, a banner should be shown that makes it possible to restore the cell for around 10 seconds. Furthermore, when no cell is focused, pressing CTRL+Z should restore the cell.

The best solution would of course be to have a history of changes to the notebook cells.

This should also work for "Delete all cells".