Give users option to display multiple workbooks in a single window like pages in a web browser
In edge, chrome, firefox, etc a user can open 1, 2, 3, or 100 pages inside one browser window, then easily switch between them. Let's bring that same simplicity to excel!
Bob LeFave commented
This should be an options setting. There are some (few) times when it's good to have multiple windows/files open, and there are (many more) times when it's good to have a single instance with multiple tabs/files open in it.
In other words: Restore MDI file handling (open all files in one window); make SDI (each spreadsheet opens in a separate window) optional. No, I'm not going to list reasons to do that - there are hundreds of comments doing that in the original thread, which you've ignored and then closed without solving. Go and read it.