Partially inspired by the SxS output comment in this issue here #142455 I sketched up a quick proposal for a notebook editor feature that I would really like.

What I would like is that if I have a notebook document open I could move outputs from it into a fully separate editor pane. In this editor pane the outputs could be reordered and scrolled separate from the main notebook document. Instead of a new editor instance this output document would be connected to the same controller as the main document so widgets and whatnot would all work as expected if different output cells are in different panes. The UI controls would all still be in the main document and when a cell is re-executed in the main document the output is updated in the supplemental output document.

This UI feels similar in execution to the interactive window to me, except that instead of a running history log it's just the notebook outputs.

Since this output document is a full editor pane it would allow the following scenarios:

• Pull one specific output (perhaps a plot with rich widgets) into the output pane and make that pane full screen to focus on just that output. Similar in some ways to Jupyter's ability to pop out a plot from the notebook document
• Place one output side by side with code. You can scroll the output document to have your output side by side, either with the cell that is generating that output or with an earlier cell
• Place one output side by side with another output. Since you can move outputs to and from the pane individually you can put a cell with say a widget slider next to the output cell that shows the effects of that widget changing in a plot.

There is a big question here of if / how we can have two different editor panes sharing a notebook controller and communications, but just leaving that slightly to the side for now to just look at the UI bits.