Hello VitoHGrind,

This macro will set the each Drop Down in the entire workbook to the first item in its list. You can place a call to this macro in either an Auto_Open procedure or the Worksheet_Open event procedure.
Sub SetDefaults()

  Dim DD As Excel.DropDown
  Dim Wks As Worksheet
  
    For Each Wks In ThisWorkbook
      If Wks.DropDowns.Count > 0 Then
        For Each DD In Wks.DropDowns
          DD.ListIndex = 1
        Next DD
      End If
    Next Wks
    
End Sub
Sincerely,
Leith Ross