'CODE 1 Ставим флажок если был один щелчок по ячейке.
Private Sub Worksheet_SelectionChange(ByVal Target As Range)
    If Target.Cells.Count > 1 Then Exit Sub
        If Not Intersect(Target, Range("A2:A100")) Is Nothing Then
            Target.Font.Name = "Marlett"
            If Target = vbNullString Then
                Target = "a"
            Else
                Target = vbNullString
            End If
        End If
End Sub
  
'CODE 2 убираем флажок по двойному щелчку по ячейке.
Private Sub Worksheet_BeforeDoubleClick(ByVal Target As Range, Cancel As Boolean)
    If Not Intersect(Target, Range("A2:A100")) Is Nothing Then
        Cancel = True 'что бы не уйти в режим редактирования.
        Target.Font.Name = "Marlett"
            If Target = vbNullString Then
                Target = "a"
            Else
                Target = vbNullString
            End If
    End If
End Sub

Private Sub Worksheet_BeforeDoubleClick(ByVal Target As Range, Cancel As Boolean)
If Not Intersect(Target, Range("A1:A1")) Is Nothing Then
    If Selection.EntireColumn.Hidden = True Then
            Columns("C:O").Select
            Selection.EntireColumn.Hidden = False
        Else
            Columns("C:O").Select
            Selection.EntireColumn.Hidden = True
    End If
End If
Cancel = True 
End Sub

    If Not Intersect(Target, Cells(4, 7)) Is Nothing Then ' навигация
        Cancel = True
          Range("GO1:HE1").Columns.Hidden = Not Range("GO1:HE1").Columns.Hidden ' скрываемые колонки
    End If

Private Sub Worksheet_BeforeDoubleClick(ByVal Target As Range, Cancel As Boolean)
 
    If Not Intersect(Target, Cells(1, 1)) Is Nothing Then
        Cancel = True
          Range("B1:O1").Columns.Hidden = Not Range("B1:O1").Columns.Hidden
          If Target.Interior.ColorIndex = 35 Then
          Target.Interior.ColorIndex = 36
          Else
          Target.Interior.ColorIndex = 35
          End If 
    End If
End Sub