diff --git a/gui/include/DragDropHelper.h b/gui/include/DragDropHelper.h
index 17103c4..30c3b5b 100644
--- a/gui/include/DragDropHelper.h
+++ b/gui/include/DragDropHelper.h
@@ -54,6 +54,7 @@ public:
     QUrl imageTemporaryUrl(const QImage &image) const;
 
     void setHightlightedDragWidget(VisualizationDragWidget *dragWidget);
+    VisualizationDragWidget *getHightlightedDragWidget() const;
 
 private:
     class DragDropHelperPrivate;
diff --git a/gui/include/Visualization/VisualizationDragDropContainer.h b/gui/include/Visualization/VisualizationDragDropContainer.h
index 6abfbc3..1b60794 100644
--- a/gui/include/Visualization/VisualizationDragDropContainer.h
+++ b/gui/include/Visualization/VisualizationDragDropContainer.h
@@ -17,7 +17,8 @@ class VisualizationDragDropContainer : public QWidget {
     Q_OBJECT
 
 signals:
-    void dropOccured(int dropIndex, const QMimeData *mimeData);
+    void dropOccuredInContainer(int dropIndex, const QMimeData *mimeData);
+    void dropOccuredOnWidget(VisualizationDragWidget *dragWidget, const QMimeData *mimeData);
 
 public:
     using AcceptMimeDataFunction = std::function<bool(const QMimeData *mimeData)>;
diff --git a/gui/include/Visualization/VisualizationZoneWidget.h b/gui/include/Visualization/VisualizationZoneWidget.h
index 3700489..f364645 100644
--- a/gui/include/Visualization/VisualizationZoneWidget.h
+++ b/gui/include/Visualization/VisualizationZoneWidget.h
@@ -85,6 +85,7 @@ private slots:
     void onVariableAboutToBeRemoved(std::shared_ptr<Variable> variable);
 
     void dropMimeData(int index, const QMimeData *mimeData);
+    void dropMimeDataOnGraph(VisualizationDragWidget *dragWidget, const QMimeData *mimeData);
 };
 
 #endif // SCIQLOP_VISUALIZATIONZONEWIDGET_H
diff --git a/gui/src/DragDropHelper.cpp b/gui/src/DragDropHelper.cpp
index 7f96d19..8806547 100644
--- a/gui/src/DragDropHelper.cpp
+++ b/gui/src/DragDropHelper.cpp
@@ -281,6 +281,11 @@ void DragDropHelper::setHightlightedDragWidget(VisualizationDragWidget *dragWidg
     impl->m_HighlightedDragWidget = dragWidget;
 }
 
+VisualizationDragWidget *DragDropHelper::getHightlightedDragWidget() const
+{
+    return impl->m_HighlightedDragWidget;
+}
+
 bool DragDropHelper::checkMimeDataForVisualization(const QMimeData *mimeData,
                                                    VisualizationDragDropContainer *dropContainer)
 {
diff --git a/gui/src/Visualization/VisualizationDragDropContainer.cpp b/gui/src/Visualization/VisualizationDragDropContainer.cpp
index f31b5e8..25e8deb 100644
--- a/gui/src/Visualization/VisualizationDragDropContainer.cpp
+++ b/gui/src/Visualization/VisualizationDragDropContainer.cpp
@@ -264,10 +264,12 @@ void VisualizationDragDropContainer::dragMoveEvent(QDragMoveEvent *event)
 
 void VisualizationDragDropContainer::dropEvent(QDropEvent *event)
 {
+    auto &helper = sqpApp->dragDropHelper();
+
     if (impl->acceptMimeData(event->mimeData())) {
-        auto dragWidget = sqpApp->dragDropHelper().getCurrentDragWidget();
+        auto dragWidget = helper.getCurrentDragWidget();
         if (impl->hasPlaceHolder()) {
-            auto &helper = sqpApp->dragDropHelper();
+            // drop where the placeHolder is located
 
             auto droppedIndex = impl->m_Layout->indexOf(&helper.placeHolder());
 
@@ -287,13 +289,22 @@ void VisualizationDragDropContainer::dropEvent(QDropEvent *event)
 
             helper.removePlaceHolder();
 
-            emit dropOccured(droppedIndex, event->mimeData());
+            emit dropOccuredInContainer(droppedIndex, event->mimeData());
         }
-        else {
-            qCWarning(LOG_VisualizationDragDropContainer())
-                << tr("VisualizationDragDropContainer::dropEvent, couldn't drop because the "
-                      "placeHolder is not found.");
-            // Q_ASSERT(false);
+        else if (helper.getHightlightedDragWidget()) {
+            // drop on the highlighted widget
+
+            auto canMerge = impl->allowMergeMimeData(event->mimeData());
+            if (canMerge) {
+                event->acceptProposedAction();
+                emit dropOccuredOnWidget(helper.getHightlightedDragWidget(), event->mimeData());
+            }
+            else {
+                qCWarning(LOG_VisualizationDragDropContainer())
+                    << tr("VisualizationDragDropContainer::dropEvent, dropping on a widget, but "
+                          "the merge is forbidden.");
+                Q_ASSERT(false);
+            }
         }
     }
     else {
diff --git a/gui/src/Visualization/VisualizationTabWidget.cpp b/gui/src/Visualization/VisualizationTabWidget.cpp
index 2bdce7f..2856324 100644
--- a/gui/src/Visualization/VisualizationTabWidget.cpp
+++ b/gui/src/Visualization/VisualizationTabWidget.cpp
@@ -70,7 +70,7 @@ VisualizationTabWidget::VisualizationTabWidget(const QString &name, QWidget *par
 
     ui->dragDropContainer->setAcceptedMimeTypes(
         {MIME_TYPE_GRAPH, MIME_TYPE_ZONE, MIME_TYPE_VARIABLE_LIST});
-    connect(ui->dragDropContainer, &VisualizationDragDropContainer::dropOccured, this,
+    connect(ui->dragDropContainer, &VisualizationDragDropContainer::dropOccuredInContainer, this,
             &VisualizationTabWidget::dropMimeData);
     ui->dragDropContainer->setAcceptMimeDataFunction([this](auto mimeData) {
         return sqpApp->dragDropHelper().checkMimeDataForVisualization(mimeData,
diff --git a/gui/src/Visualization/VisualizationZoneWidget.cpp b/gui/src/Visualization/VisualizationZoneWidget.cpp
index 2f1642e..9dff6bb 100644
--- a/gui/src/Visualization/VisualizationZoneWidget.cpp
+++ b/gui/src/Visualization/VisualizationZoneWidget.cpp
@@ -91,8 +91,11 @@ VisualizationZoneWidget::VisualizationZoneWidget(const QString &name, QWidget *p
         return sqpApp->dragDropHelper().checkMimeDataForVisualization(mimeData,
                                                                       ui->dragDropContainer);
     });
-    connect(ui->dragDropContainer, &VisualizationDragDropContainer::dropOccured, this,
+
+    connect(ui->dragDropContainer, &VisualizationDragDropContainer::dropOccuredInContainer, this,
             &VisualizationZoneWidget::dropMimeData);
+    connect(ui->dragDropContainer, &VisualizationDragDropContainer::dropOccuredOnWidget, this,
+            &VisualizationZoneWidget::dropMimeDataOnGraph);
 
     // 'Close' options : widget is deleted when closed
     setAttribute(Qt::WA_DeleteOnClose);
@@ -381,6 +384,31 @@ void VisualizationZoneWidget::dropMimeData(int index, const QMimeData *mimeData)
     }
 }
 
+void VisualizationZoneWidget::dropMimeDataOnGraph(VisualizationDragWidget *dragWidget,
+                                                  const QMimeData *mimeData)
+{
+    auto graphWidget = qobject_cast<VisualizationGraphWidget *>(dragWidget);
+    if (!graphWidget) {
+        qCWarning(LOG_VisualizationZoneWidget())
+            << tr("VisualizationZoneWidget::dropMimeDataOnGraph, dropping in an unknown widget, "
+                  "drop aborted");
+        Q_ASSERT(false);
+        return;
+    }
+
+    if (mimeData->hasFormat(MIME_TYPE_VARIABLE_LIST)) {
+        auto variables = sqpApp->variableController().variablesForMimeData(
+            mimeData->data(MIME_TYPE_VARIABLE_LIST));
+        for (const auto &var : variables) {
+            graphWidget->addVariable(var, graphWidget->graphRange());
+        }
+    }
+    else {
+        qCWarning(LOG_VisualizationZoneWidget())
+            << tr("VisualizationZoneWidget::dropMimeDataOnGraph, unknown MIME data received.");
+    }
+}
+
 void VisualizationZoneWidget::VisualizationZoneWidgetPrivate::dropGraph(
     int index, VisualizationZoneWidget *zoneWidget)
 {