I would say a second optional section, where you can also select select which cells you would like to override and the tool generates some placeholder code for redefining the cell value. The cell selector should have an option for selecting the width, and people choose one that use the snippet above modifying the standard Library
This section needs to be redone. redefine() expects a cell *definition*, i.e. a function that injects all inputs into the cell's scope and returns the actual value. I'd also expect cells with inputs to be more common, so our examples should probably focus on that.