実行コード

Sub a()
  Call Set選択されている図形の名前("test")
End Sub
Sub b()
  Call 指定された名前の図形にテキストデータ書き込み("test", "内容")
End Sub
Sub c()
  Call 指定された名前の図形にテキストデータ読み込み("test")
End Sub

図形の名前の設定/取得

Sub Get選択されている図形の名前()
  Dim shp As Shape

  With ActiveWindow.Selection

    If .Type = ppSelectionNone Or _
      .Type = ppSelectionSlides Then Exit Sub

    For Each shp In .ShapeRange
      Debug.Print shp.Name
    Next shp

  End With

End Sub
Sub Set選択されている図形の名前(ShapeName)
  Dim shp As Shape

  With ActiveWindow.Selection

    If .Type = ppSelectionNone Or _
      .Type = ppSelectionSlides Then Exit Sub

    For Each shp In .ShapeRange
      shp.Name = ShapeName
    Next shp

  End With

End Sub

指定名の図形を狙って読み書き

Sub 指定された名前の図形にテキストデータ書き込み(ShapeName, 書き込む内容)
  Dim prs As Presentation
  Dim sld As Slide
  Dim shp As Shape
  
  Set prs = PowerPoint.ActivePresentation
  
  For Each sld In prs.Slides
    Debug.Print sld.Name
    For Each shp In sld.Shapes
      If shp.Name = ShapeName Then
        shp.TextFrame.TextRange.Text = 書き込む内容
      End If
    Next
  Next

End Sub
Sub 指定された名前の図形にテキストデータ読み込み(ShapeName)
  Dim prs As Presentation
  Dim sld As Slide
  Dim shp As Shape
  
  Set prs = PowerPoint.ActivePresentation
  
  For Each sld In prs.Slides
    Debug.Print sld.Name
    For Each shp In sld.Shapes
      If shp.Name = ShapeName Then
        Debug.Print shp.TextFrame.TextRange.Text
      End If
    Next
  Next

End Sub