diff --git a/README.md b/README.md
index 56a7679..9da5645 100644
--- a/README.md
+++ b/README.md
@@ -33,6 +33,9 @@ Go to `System Settings` -> `Window Management` -> `KWin Scripts` -> `Get New Scr
 
 And then search for `kwin-maximize-to-new-desktop`.
 
+Note: __To get the configuration panel fully working, see [this](#no-configuration-button-available-in-the-kwin-scripts-entry)
+and [this](#blank-window-class-blacklist-in-configuration)__
+
 ### Install directly
 
 Download the latest release from KDE [store][store], and run
@@ -41,6 +44,9 @@ Download the latest release from KDE [store][store], and run
 plasmapkg2 --install kwin-maxmize-to-new-desktop-0.2.0.tar.gz
 ```
 
+Note: __To get the configuration panel fully working, see [this](#no-configuration-button-available-in-the-kwin-scripts-entry)
+and [this](#window-class-blacklist-in-configuration-is-blank)__
+
 ## Tips
 
 ### Get window's class for the blacklist
@@ -60,6 +66,14 @@ mkdir -p ~/.local/share/kservices5
 ln -s ~/.local/share/kwin/scripts/max2NewVirtualDesktop/metadata.desktop ~/.local/share/kservices5/max2NewVirtualDesktop.desktop
 ```
 
+### Blank window class blacklist in configuration
+
+You need to install an additional package called `kdesignerplugin` ([link](https://github.com/KDE/kdesignerplugin)),
+which makes it possible to use KEditListWidget.
+
+* For ArchLinux: `pacman -Syu kdesignerplugin`.
+* For Ubuntu and alike: `apt install kdesignerplugin`.
+
 ### Configuration not picked up by the script after changing
 
 Log out and log in again.
diff --git a/contents/ui/config.ui b/contents/ui/config.ui
index daafbb8..dae9699 100644
--- a/contents/ui/config.ui
+++ b/contents/ui/config.ui
@@ -87,7 +87,7 @@
     </widget>
    </item>
    <item row="2" column="1">
-    <widget class="KComboBox" name="kcfg_newDesktopPosition">
+    <widget class="QComboBox" name="kcfg_newDesktopPosition">
      <item>
       <property name="text">
        <string>Right Most</string>
@@ -144,7 +144,7 @@
     </widget>
    </item>
    <item row="1" column="1">
-    <widget class="KComboBox" name="kcfg_trigger">
+    <widget class="QComboBox" name="kcfg_trigger">
      <item>
       <property name="text">
        <string>Fullscreen Only</string>
@@ -197,11 +197,6 @@
   </layout>
  </widget>
  <customwidgets>
-  <customwidget>
-   <class>KComboBox</class>
-   <extends>QComboBox</extends>
-   <header>kcombobox.h</header>
-  </customwidget>
   <customwidget>
    <class>KEditListWidget</class>
    <extends>QWidget</extends>