mdd_client/build/resources/main/mdd/client/main.fxml

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>

<VBox maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/10.0.2-internal" xmlns:fx="http://javafx.com/fxml/1" fx:controller="mdd.client.FXMLDocumentController">
   <children>
       <MenuBar>
           <Menu fx:id="mMain" text="Main">
               <MenuItem text="Exit" />
           </Menu>

           <Menu fx:id="mAbout" text="About">
           </Menu>
       </MenuBar>
      <SplitPane fx:id="sPane" dividerPositions="0.2, 0.8" prefHeight="${sPane.parent.height}" prefWidth="600.0">
        <items>
            <Accordion>
              <panes>
                <TitledPane animated="false" text="untitled 1">
                  <content>
                    <AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="180.0" prefWidth="100.0" />
                  </content>
                </TitledPane>
                <TitledPane animated="false" text="untitled 2">
                  <content>
                    <AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="180.0" prefWidth="100.0" />
                  </content>
                </TitledPane>
                <TitledPane animated="false" text="untitled 3">
                  <content>
                    <AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="180.0" prefWidth="100.0" />
                  </content>
                </TitledPane>
              </panes>
            </Accordion>
            <TabPane fx:id="tabPane" prefHeight="238.0" prefWidth="400.0" tabClosingPolicy="UNAVAILABLE">

            </TabPane>
            <Accordion>
              <panes>
                <TitledPane animated="false" text="untitled 1">
                  <content>
                    <AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="180.0" prefWidth="100.0" />
                  </content>
                </TitledPane>
                <TitledPane animated="false" text="untitled 2">
                  <content>
                    <AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="180.0" prefWidth="100.0" />
                  </content>
                </TitledPane>
                <TitledPane animated="false" text="untitled 3">
                  <content>
                    <AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="180.0" prefWidth="100.0" />
                  </content>
                </TitledPane>
              </panes>
            </Accordion>
        </items>
      </SplitPane>
   </children>
</VBox>