Set Excel to search within entire workbook by default
Solution 1:
You can do this with a Workbook_Open macro in the ThisWorkbook module, like so:
Private Sub Workbook_Open()
Application.CommandBars.FindControl(ID:=1849).Execute
SendKeys "%(t)%(h)W~{ESC}"
End Sub
This will set it for your session for the workbook you're in.
To have this always be the default you need to create a Personal Macro Workbook.
Solution 2:
I included a modification so it will work if your Excel is in Spanish (like mine)
Private Sub Workbook_Open()
Dim lCountryCode As Long
lCountryCode = Application.International(xlCountryCode)
Application.CommandBars.FindControl(ID:=1849).Execute
Select Case lCountryCode
Case 34 'spanish
SendKeys "%(p)%(D)L~{ESC}"
Case Else 'default english
SendKeys "%(t)%(h)W~{ESC}"
End Select
End Sub