diff --git a/src/calibre/gui2/preferences/template_functions.py b/src/calibre/gui2/preferences/template_functions.py
index a9aca83226..a5d0a3b974 100644
--- a/src/calibre/gui2/preferences/template_functions.py
+++ b/src/calibre/gui2/preferences/template_functions.py
@@ -168,6 +168,8 @@ class ConfigWidget(ConfigWidgetBase, Ui_Form):
                 self.db.prefs['user_template_functions'] = []
             raise AbortInitialize()
 
+        self.show_only_user_defined.setChecked(True)
+        self.show_only_user_defined.stateChanged.connect(self.show_only_user_defined_changed)
         self.build_function_names_box()
         self.function_name.currentIndexChanged.connect(self.function_index_changed)
         self.function_name.editTextChanged.connect(self.function_name_edited)
@@ -222,6 +224,9 @@ class ConfigWidget(ConfigWidgetBase, Ui_Form):
 
     # Python function tab
 
+    def show_only_user_defined_changed(self, state):
+        self.build_function_names_box()
+
     def enable_replace_button(self):
         self.replace_button.setEnabled(self.delete_button.isEnabled())
 
@@ -233,23 +238,35 @@ class ConfigWidget(ConfigWidgetBase, Ui_Form):
         self.create_button.setEnabled(False)
         self.delete_button.setEnabled(False)
 
+    def function_type_string(self, name):
+        if name in self.builtins:
+            return ' -- ' + _('Built-in function')
+        else:
+            return ' -- ' + _('User function')
+
     def build_function_names_box(self, scroll_to=''):
         self.function_name.blockSignals(True)
-        func_names = sorted(self.funcs)
+        if self.show_only_user_defined.isChecked():
+            func_names = sorted([k for k in self.funcs if k not in self.builtins])
+        else:
+            func_names = sorted(self.funcs)
         self.function_name.clear()
         self.function_name.addItem('')
-        self.function_name.addItems(func_names)
+        scroll_to_index = 0
+        for idx,n in enumerate(func_names):
+            self.function_name.addItem(n + self.function_type_string(n))
+            self.function_name.setItemData(idx+1, n)
+            if scroll_to and n == scroll_to:
+                scroll_to_index = idx+1
         self.function_name.setCurrentIndex(0)
         self.function_name.blockSignals(False)
-        if scroll_to:
-            idx = self.function_name.findText(scroll_to)
-            if idx >= 0:
-                self.function_name.setCurrentIndex(idx)
-                if scroll_to not in self.builtins:
-                    self.delete_button.setEnabled(True)
+        if scroll_to_index:
+            self.function_name.setCurrentIndex(scroll_to_index)
+            if scroll_to not in self.builtins:
+                self.delete_button.setEnabled(True)
 
     def delete_button_clicked(self):
-        name = str(self.function_name.currentText())
+        name = str(self.function_name.itemData(self.function_name.currentIndex()))
         if name in self.builtins:
             error_dialog(self.gui, _('Template functions'),
                          _('You cannot delete a built-in function'), show=True)
@@ -267,6 +284,11 @@ class ConfigWidget(ConfigWidgetBase, Ui_Form):
     def create_button_clicked(self, use_name=None):
         self.changed_signal.emit()
         name = use_name if use_name else str(self.function_name.currentText())
+        name = name.split(' -- ')[0]
+        if not name:
+            error_dialog(self.gui, _('Template functions'),
+                         _('Name cannot be empty'), show=True)
+            return
         if name in self.funcs:
             error_dialog(self.gui, _('Template functions'),
                          _('Name %s already used')%(name,), show=True)
@@ -299,14 +321,20 @@ class ConfigWidget(ConfigWidgetBase, Ui_Form):
                          det_msg=traceback.format_exc())
 
     def function_name_edited(self, txt):
+        txt = txt.split(' -- ')[0]
+        if txt not in self.funcs:
+            self.function_name.blockSignals(True)
+            self.function_name.setEditText(txt)
+            self.function_name.blockSignals(False)
         self.documentation.setReadOnly(False)
         self.argument_count.setReadOnly(False)
         self.create_button.setEnabled(True)
         self.replace_button.setEnabled(False)
+        self.delete_button.setEnabled(False)
         self.program.setReadOnly(False)
 
     def function_index_changed(self, idx):
-        txt = self.function_name.currentText()
+        txt = self.function_name.itemData(idx)
         self.create_button.setEnabled(False)
         if not txt:
             self.argument_count.clear()
@@ -335,7 +363,7 @@ class ConfigWidget(ConfigWidgetBase, Ui_Form):
         self.replace_button.setEnabled(False)
 
     def replace_button_clicked(self):
-        name = str(self.function_name.currentText())
+        name = str(self.function_name.itemData(self.function_name.currentIndex()))
         self.delete_button_clicked()
         self.create_button_clicked(use_name=name)
 
diff --git a/src/calibre/gui2/preferences/template_functions.ui b/src/calibre/gui2/preferences/template_functions.ui
index f68144a369..4c8690da2d 100644
--- a/src/calibre/gui2/preferences/template_functions.ui
+++ b/src/calibre/gui2/preferences/template_functions.ui
@@ -125,6 +125,19 @@
          <item row="0" column="1" colspan="2" rowspan="2">
           <widget class="QTextBrowser" name="textBrowser"/>
          </item>
+         <item row="3" column="1">
+          <widget class="QCheckBox" name="show_only_user_defined">
+           <property name="text">
+            <string>Show &amp;only user defined template functions</string>
+           </property>
+           <property name="toolTip">
+            <string>&lt;p&gt;If checked the 'Function' box will show only user defined
+template functions. If unchecked the box will show both system and user defined
+functions. Unchecking can be useful for copying source of a system function to create
+a new related user defined function.&lt;/p&gt;</string>
+           </property>
+          </widget>
+         </item>
          <item row="2" column="0">
           <widget class="QLabel" name="label_2">
            <property name="text">
@@ -145,7 +158,7 @@
            </property>
           </widget>
          </item>
-         <item row="3" column="0">
+         <item row="4" column="0">
           <widget class="QLabel" name="label_3">
            <property name="toolTip">
             <string/>
@@ -158,7 +171,7 @@
            </property>
           </widget>
          </item>
-         <item row="3" column="1">
+         <item row="4" column="1">
           <widget class="QSpinBox" name="argument_count">
            <property name="toolTip">
             <string>Set this to -1 if the function takes a variable number of arguments</string>
@@ -168,10 +181,10 @@
            </property>
           </widget>
          </item>
-         <item row="4" column="1">
+         <item row="5" column="1">
           <widget class="QTextEdit" name="documentation"/>
          </item>
-         <item row="4" column="0">
+         <item row="5" column="0">
           <widget class="QLabel" name="label_4">
            <property name="text">
             <string>D&amp;ocumentation:</string>
@@ -184,7 +197,7 @@
            </property>
           </widget>
          </item>
-         <item row="5" column="1">
+         <item row="6" column="1">
           <layout class="QHBoxLayout" name="horizontalLayout_2">
            <item>
             <widget class="QPushButton" name="clear_button">