--- a/editors/ConfTreeNodeEditor.py	Thu Jul 22 12:03:34 2021 +0200
+++ b/editors/ConfTreeNodeEditor.py	Fri Jul 23 13:15:19 2021 +0200
@@ -385,7 +385,7 @@
                                            element_infos["children"],
                                            element_path)
             else:
-                boxsizer = wx.FlexGridSizer(cols=3, rows=1)
+                boxsizer = wx.FlexGridSizer(cols=4, rows=1)
                 boxsizer.AddGrowableCol(1)
                 flags = (wx.GROW | wx.BOTTOM | wx.LEFT | wx.RIGHT)
                 if first:
@@ -472,8 +472,9 @@
 
                 else:
                     if element_infos["type"] == "boolean":
-                        checkbox = wx.CheckBox(self.ParamsEditor, size=wx.Size(17, 25))
-                        boxsizer.AddWindow(checkbox)
+                        checkbox = wx.CheckBox(self.ParamsEditor)
+                        boxsizer.AddWindow(checkbox, border=5,
+                                   flag=wx.ALIGN_CENTER_VERTICAL | wx.RIGHT)
                         if element_infos["value"] is not None:
                             checkbox.SetValue(element_infos["value"])
                         checkbox.Bind(wx.EVT_CHECKBOX,
@@ -526,6 +527,16 @@
                         textctrl.Bind(wx.EVT_TEXT_ENTER, callback)
                         textctrl.Bind(wx.EVT_TEXT, callback)
                         textctrl.Bind(wx.EVT_KILL_FOCUS, callback)
+
+                if not isinstance(element_infos["type"], list) and element_infos["use"] == "optional":
+                    bt = wx.BitmapButton(self.ParamsEditor, 
+                        bitmap=wx.ArtProvider.GetBitmap(wx.ART_UNDO, wx.ART_TOOLBAR, (16,16)),
+                        style=wx.BORDER_NONE)
+                    self.Bind(wx.EVT_BUTTON, 
+                              self.GetResetFunction(element_path),
+                              bt)
+
+                    boxsizer.AddWindow(bt)
             first = False
         sizer.Layout()
         self.RefreshScrollbars()
@@ -590,6 +601,13 @@
             event.Skip()
         return OnTextCtrlChanged
 
+    def GetResetFunction(self, path):
+        def OnResetBt(event):
+            res = self.SetConfNodeParamsAttribute(path, None)
+            wx.CallAfter(self.RefreshView)
+            event.Skip()
+        return OnResetBt
+
     def GetCheckBoxCallBackFunction(self, chkbx, path):
         def OnCheckBoxChanged(event):
             res = self.SetConfNodeParamsAttribute(path, chkbx.IsChecked())

--- a/xmlclass/xmlclass.py	Thu Jul 22 12:03:34 2021 +0200
+++ b/xmlclass/xmlclass.py	Fri Jul 23 13:15:19 2021 +0200
@@ -1522,7 +1522,7 @@
                     raise ValueError("Wrong path!")
                 if attributes[parts[0]]["attr_type"]["basename"] == "boolean":
                     setattr(self, parts[0], value)
-                elif attributes[parts[0]]["use"] == "optional" and value == "":
+                elif attributes[parts[0]]["use"] == "optional" and value == None:
                     if "default" in attributes[parts[0]]:
                         setattr(self, parts[0],
                                 attributes[parts[0]]["attr_type"]["extract"](