A family of Microsoft presentation graphics products that offer tools for creating presentations and adding graphic effects like multimedia objects and special effects with text.
There's no way I know to do that out of the box in PPT.
If you are prespared to use some simple code it would rewrite the TOC slide in seconds.
Something based on this.
Sub Mk_TOC()
Dim L As Long
Dim osld As Slide
' the slides need to have a Title with the text needed for the TOC
With ActivePresentation.Slides(1).Shapes(2).TextFrame.TextRange
.Text = ""
For L = 2 To 6 'change if more or fewer slides
Set osld = ActivePresentation.Slides(L)
.Text = .Text & osld.SlideIndex - 1 & ". " & osld.Shapes.Title.TextFrame.TextRange & vbCrLf
Next L
End With
End Sub