Hello,
Please be informed that the feature in the screenshot you have provided was present in older version of Excel application. Excel 2013 onwards Single Document Interface (SDI) was introduced. SDI is a method of organizing graphical user interface (UI) applications into individual windows that the operating system window manager handles separately. From Excel 2013, each Excel window can contain only one workbook, and each has its own ribbon UI. By default when you open a new workbook, it will be displayed in another Excel window, even though it is the same Excel instance.
Multiple Document Interface feature was available up to Excel 2010, in which a single parent window is used to contain multiple nested child windows, with only the parent window having a menu or tool bar. Until Excel 2010, each workbook in a single instance of Excel utilizes a common ribbon UI.
I hope the above information helps. Let us know if you need further assistance.
Thank you.