diff --git a/src/mainwindow.cpp b/src/mainwindow.cpp
--- a/src/mainwindow.cpp
+++ b/src/mainwindow.cpp
@@ -104,12 +104,29 @@ MainWindow::MainWindow(QWidget *parent) 
     tbMenu->addAction(ui->plotToolBar->toggleViewAction());
     tbMenu->addAction(portControl.toolBar()->toggleViewAction());
 
+    // init secondary plot menu
+    auto group = new QActionGroup(this);
+    group->addAction(ui->actionVertical);
+    group->addAction(ui->actionHorizontal);
+
     // init UI signals
 
     // Secondary plot menu signals
     connect(ui->actionBarPlot, &QAction::triggered,
             this, &MainWindow::showBarPlot);
 
+    connect(ui->actionVertical, &QAction::triggered,
+            [this](bool checked)
+            {
+                if (checked) ui->splitter->setOrientation(Qt::Vertical);
+            });
+
+    connect(ui->actionHorizontal, &QAction::triggered,
+            [this](bool checked)
+            {
+                if (checked) ui->splitter->setOrientation(Qt::Horizontal);
+            });
+
     // Help menu signals
     QObject::connect(ui->actionHelpAbout, &QAction::triggered,
               &aboutDialog, &QWidget::show);
diff --git a/src/mainwindow.ui b/src/mainwindow.ui
--- a/src/mainwindow.ui
+++ b/src/mainwindow.ui
@@ -129,8 +129,8 @@
     </property>
     <addaction name="actionBarPlot"/>
     <addaction name="separator"/>
+    <addaction name="actionHorizontal"/>
     <addaction name="actionVertical"/>
-    <addaction name="actionHorizontal"/>
    </widget>
    <addaction name="menuFile"/>
    <addaction name="menuSecondary"/>
@@ -264,6 +264,9 @@
    <property name="checkable">
     <bool>true</bool>
    </property>
+   <property name="checked">
+    <bool>true</bool>
+   </property>
    <property name="text">
     <string>Horizontal</string>
    </property>