If you would like to enable Shared Workbook option, here's a way to add it to Excel Quick Access Toolbar. It is hidden under Excel Options.

If you, the user wants to include a particular command in the Quick Access toolbar, you must add the command to it. On the Quick Access Toolbar, you can switch the order of the commands if you desire.

For example, you can't add a button to set a specific line spacing value. If you can't add the button, no option to "Add to Quick Access Toolbar" will appear when you right-click the ribbon.