Suppose that someone does not have access to MATLAB, but does to Excel. Could they edit a variable in an Excel sheet, send that sheet to me, and once I upload to it to the Current Folder in MATLAB, have those modifications show up in the workspace?
Yes, they can give you data in whatever form you like - text file, csv file, xlsx file, etc. Then you can read in the file and use that variable. When you read them in, they will show up in the workspace.