Excel Spread Sheet

You can add the spreadsheet to the Dock where it will be available to open at any time.

Also you can add it to any Finder's toolbar like this:

However, you can add it to Safari's Bookmark bar by dragging it into the bar:

But when you click on the item in the Bookmark bar it just opens a Finder window where the file is located. It doesn't open the file in Excel. That takes an additional double click on the file.

You can create an alias to it (or any file for that matter) and drag the resulting icon to wherever you would like it to be.

That's only one suggestion. There are probably a dozen more, any one of which might be more useful to you. For additional reading, Get to know the Finder on your Mac - Apple Support.

Where is the bookmark tab? If you mean Safari Bookmarks, they are designed to bookmark web pages. It wouldn't make sense to have one for a spreadsheet.

Bookmark webpages that you want to revisit in Safari on Mac ...

If that's not what you mean then explain where you would like that bookmark to appear.

if you mean safari bookmark then it only bookmark urls I believe