Sub ScratchMacro()
'A basic Word Macro coded by Gregory K. Maxey
Dim ftNote As Footnote
Dim supLetter As String
  supLetter = "a"
  Set ftNote = ActiveDocument.Footnotes(1)
  With ftNote
    .Range.Characters.First.Previous.Delete
    .Range = supLetter & " " & .Range
    .Range.Characters.First.Font.Superscript = True
  End With
lbl_Exit:
  Exit Sub
End Sub

Sub ScratchMacro()
  'Here is your code.  If you try to run it, you will see it does nothing but error
  With ftNote.Range
    .InsertBefore supLetter 'i.e. the letter a
    .Characters(1).Font.Superscript = True
  End With
lbl_Exit:
  Exit Sub
End Sub
Sub ScratchMacro2()
'Here is your code modified with variables declared and defined.
'No erorrs and doing what you decribed.
Dim ftNote As Footnote
Dim supLetter As String
  Set ftNote = ActiveDocument.Footnotes(1)
  supLetter = "a"
  With ftNote.Range
    .InsertBefore supLetter 'i.e. the letter a
    .Characters(1).Font.Superscript = True
  End With
  'As you see, this does nothing to the actual reference in the document body.
lbl_Exit:
  Exit Sub
End Sub
Sub ScratchMacro3()
'A basic Word Macro coded by Gregory K. Maxey
'This is my code. It gives the illusion that the reference number has been changed from 1 to 1a, but
'has no affect on the actual reference number in the document body.
Dim ftNote As Footnote
Dim supLetter As String
  supLetter = "a"
  Set ftNote = ActiveDocument.Footnotes(1)
  With ftNote
    .Range.Characters.First.Previous.Delete
    .Range = supLetter & " " & .Range
    .Range.Characters.First.Font.Superscript = True
  End With
lbl_Exit:
  Exit Sub
End Sub

With ftNote.range
    ActiveDocument.range(.start - 1, .End).InsertBefore supLetter
End With

Sub ScratchMacro3()
'A basic Word Macro coded by Gregory K. Maxey
Dim ftNote As Footnote
Dim supLetter As String
  supLetter = "a"
  For Each ftNote In ActiveDocument.Footnotes
    With ftNote
      .Range.Characters.First.Previous.Delete
      .Range = supLetter & " " & .Range
      .Range.Characters.First.Font.Superscript = True
    End With
  Next
lbl_Exit:
  Exit Sub
End Sub

Sub InsertFootnote()
Dim Rng As Range: Set Rng = Selection.Range
Application.Dialogs(wdDialogInsertFootnote).Execute
Rng.End = Rng.End + 1: Rng.InsertAfter "a": Rng.Style = wdStyleFootnoteReference
Selection.Start = Selection.Start - 1
Set Rng = Selection.Range: Rng.Collapse wdCollapseStart
Rng.Start = Rng.Start - 1: Rng.InsertAfter "a": Rng.Style = wdStyleFootnoteReference
Selection.Collapse wdCollapseEnd
If ActiveWindow.ActivePane.View.Type = wdPrintView Or ActiveWindow. _
  ActivePane.View.Type = wdWebView Or ActiveWindow.ActivePane.View.Type = wdPrintPreview Then
  ActiveWindow.View.SeekView = wdSeekFootnotes
Else
  ActiveWindow.View.SplitSpecial = wdPaneFootnotes
End If
End Sub