Feature request: Show status information about running notebooks

In a shared environment, it would be useful to see more status information about a running notebook, such as:

• is the notebook currently executing?
• how long has it been since the notebook was executed?
• (if possible) is the notebook currently being viewed?

This would assist decisions to close notebooks to free up resources.

I'll add... highlight which cell is it currently working on, so it's easier to find which cell to stop and comment out while debugging.

I'll add... highlight which cell is it currently working on, so it's easier to find which cell to stop and comment out while debugging.

This should probably be its own issue, though I would agree it's too subtle right now.