User Configuration > Administrative Templates > Microsoft Excel 2016 > Excel Options > Advanced
User
HKCU\software\policies\microsoft\office\16.0\excel\options\binaryoptions
This policy setting sets the "Edit directly in cell" option found under File tab | Options | Advanced | Editing Options. If you enable or do not configure this policy setting, Excel will allow editing directly in the cell This is the default behavior. If you disable this policy setting, Excel will not allow editing to be done directly in the cell.