Good day John,
we’d an attempt to create a similar behavior because, as you wrote, this is the way things are handled in Excel, but… it’s a bunch of lines to be written. Our CTO just told me that he had an example like this on an older version of Handsontable but it did not work completely so we’ve abandoned this idea.
One thing’s sure - you’d need to create a custom renderer. None of our default renderers allow to extend the text outside the cell.
If this functionality is on your priority list I can schedule a consulting session for you. It’s a commercial service but we can cut down the cost a bit if we find it useful for the Handsontable as a product.