A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
If you hold down Shift while clicking the close button in the upper right corner of any open workbook, it acts as Close All. You'll be prompted to save any modified workbooks, with an option to save them all:
To minimize all workbooks, you could add the following macro to your personal macro workbook Personal.xlsb:
Sub MinimizeAll()
Dim win As Window
On Error Resume Next
For Each win In Application.Windows
win.WindowState = xlMinimized
Next win
End Sub
If desired, you can assign this macro to a custom keyboard shortcut and/or to a Quick Access Toolbar button.