For using thumbnails, insert note about extra action required.

src/settings/ThumbnailsSettings.ui

@@ -31,41 +31,60 @@
      </property>
     </widget>
    </item>
-   <item row="1" column="0">
-    <widget class="QLabel" name="label_2">
-     <property name="text">
-      <string>Activation:</string>
-     </property>
-    </widget>
-   </item>
-   <item row="1" column="1">
+   <item row="2" column="1">
     <widget class="QLabel" name="label_5">
      <property name="text">
       <string>Mouse hover plus</string>
      </property>
     </widget>
    </item>
-   <item row="2" column="1">
+   <item row="3" column="1">
     <widget class="QCheckBox" name="kcfg_ThumbnailShift">
      <property name="text">
       <string>Shift</string>
      </property>
     </widget>
    </item>
-   <item row="3" column="1">
+   <item row="4" column="1">
     <widget class="QCheckBox" name="kcfg_ThumbnailAlt">
      <property name="text">
       <string>Alt</string>
      </property>
     </widget>
    </item>
-   <item row="4" column="1">
+   <item row="5" column="1">
     <widget class="QCheckBox" name="kcfg_ThumbnailCtrl">
      <property name="text">
       <string>Ctrl</string>
      </property>
     </widget>
    </item>
+   <item row="1" column="0" colspan="2">
+    <widget class="QLabel" name="label_3">
+     <property name="text">
+      <string>&lt;html&gt;&lt;head/&gt;&lt;body&gt;&lt;p&gt;&lt;span style=&quot; font-weight:600;&quot;&gt;Remember&lt;/span&gt;: to enable &lt;span style=&quot; font-weight:600;&quot;&gt;Mouse-&amp;gt;Miscellaneous-&amp;gt;Underline&lt;/span&gt;&lt;span style=&quot; font-weight:600;&quot;&gt;files&lt;/span&gt; inside your profile mouse settings&lt;/p&gt;&lt;/body&gt;&lt;/html&gt;</string>
+     </property>
+     <property name="textFormat">
+      <enum>Qt::RichText</enum>
+     </property>
+     <property name="wordWrap">
+      <bool>true</bool>
+     </property>
+     <property name="margin">
+      <number>0</number>
+     </property>
+    </widget>
+   </item>
+   <item row="2" column="0">
+    <widget class="QLabel" name="label_2">
+     <property name="text">
+      <string>Activation:</string>
+     </property>
+     <property name="margin">
+      <number>0</number>
+     </property>
+    </widget>
+   </item>
   </layout>
  </widget>
  <resources/>