diff -r c89fc366bebd -r 0ffb41625592 controls/PouInstanceVariablesPanel.py
--- a/controls/PouInstanceVariablesPanel.py	Thu Sep 02 21:36:29 2021 +0200
+++ b/controls/PouInstanceVariablesPanel.py	Thu Sep 02 22:18:14 2021 +0200
@@ -132,7 +132,7 @@
 
         self.ParentButton = wx.lib.buttons.GenBitmapButton(
             self, bitmap=GetBitmap("top"), size=wx.Size(28, 28), style=wx.NO_BORDER)
-        self.ParentButton.SetToolTipString(_("Parent instance"))
+        self.ParentButton.SetToolTip(_("Parent instance"))
         self.Bind(wx.EVT_BUTTON, self.OnParentButtonClick,
                   self.ParentButton)
 
@@ -142,7 +142,7 @@
 
         self.DebugButton = wx.lib.buttons.GenBitmapButton(
             self, bitmap=GetBitmap("debug_instance"), size=wx.Size(28, 28), style=wx.NO_BORDER)
-        self.DebugButton.SetToolTipString(_("Debug instance"))
+        self.DebugButton.SetToolTip(_("Debug instance"))
         self.Bind(wx.EVT_BUTTON, self.OnDebugButtonClick,
                   self.DebugButton)
 
@@ -175,15 +175,15 @@
                 self.DebugButtonCallback, self.DebugButtonDClickCallback)}
 
         buttons_sizer = wx.FlexGridSizer(cols=3, hgap=0, rows=1, vgap=0)
-        buttons_sizer.AddWindow(self.ParentButton)
-        buttons_sizer.AddWindow(self.InstanceChoice, flag=wx.GROW)
-        buttons_sizer.AddWindow(self.DebugButton)
+        buttons_sizer.Add(self.ParentButton)
+        buttons_sizer.Add(self.InstanceChoice, flag=wx.GROW)
+        buttons_sizer.Add(self.DebugButton)
         buttons_sizer.AddGrowableCol(1)
         buttons_sizer.AddGrowableRow(0)
 
         main_sizer = wx.FlexGridSizer(cols=1, hgap=0, rows=2, vgap=0)
-        main_sizer.AddSizer(buttons_sizer, flag=wx.GROW)
-        main_sizer.AddWindow(self.VariablesList, flag=wx.GROW)
+        main_sizer.Add(buttons_sizer, flag=wx.GROW)
+        main_sizer.Add(self.VariablesList, flag=wx.GROW)
         main_sizer.AddGrowableCol(0)
         main_sizer.AddGrowableRow(1)