diff --git a/src/appproject.cpp b/src/appproject.cpp
index fd5584f2..5556f6dc 100644
--- a/src/appproject.cpp
+++ b/src/appproject.cpp
@@ -606,6 +606,12 @@ void AppProject::closeProject()
     // Close any remaining windows (for example split auto-clones).
     _mdiArea->closeAllSubWindows();
 
+    // Force immediate destruction of MDI subwindows (WA_DeleteOnClose uses
+    // deleteLater, so without this their destructors run after new forms are
+    // already created, causing deviceIdAdded/unitMapAdded signals to be
+    // suppressed for the newly opened project).
+    QCoreApplication::sendPostedEvents(nullptr, QEvent::DeferredDelete);
+
     const auto deleteClosedForms = [this](auto&& shouldDelete) {
         const auto snapshot = _closedForms;
         for (auto* frm : snapshot) {
@@ -628,6 +634,8 @@ void AppProject::closeProject()
 
     _closedForms.clear();
     _mbServer.clearAddressSpace();
+    _mbServer.clearDescriptions();
+    _mbServer.clearTimestamps();
     _dataCounter        = 0;
     _trafficCounter     = 0;
     _scriptCounter      = 0;
@@ -1687,11 +1695,11 @@ void AppProject::loadProject(const QString& filename)
     if(!file.open(QFile::ReadOnly))
         return;
 
-    _projectFilename = QFileInfo(filename).absoluteFilePath();
-    emit projectOpened(_projectFilename);
-
-    _mbServer.clearDescriptions();
-    _mbServer.clearTimestamps();
+    if (_projectFilename.isEmpty()) {
+        setSavePath(QFileInfo(filename).absoluteDir().absolutePath());
+        _projectFilename = QFileInfo(filename).absoluteFilePath();
+        emit projectOpened(_projectFilename);
+    }
 
     ModbusDefinitions defs;
     QList<ConnectionDetails> conns;
@@ -1773,20 +1781,6 @@ void AppProject::loadProject(const QString& filename)
                             _mdiArea->setSplitViewEnabled(splitView);
                         viewPreparedForForms = true;
                     }
-
-                    _mdiArea->closeAllSubWindows();
-                    // Force immediate destruction of MDI subwindows (WA_DeleteOnClose uses
-                    // deleteLater, so without this their destructors run after new forms are
-                    // already created, causing deviceIdAdded/unitMapAdded signals to be
-                    // suppressed for the newly opened project).
-                    QCoreApplication::sendPostedEvents(nullptr, QEvent::DeferredDelete);
-                    // Clean up forms that were already closed (hidden)
-                    const auto closed = _closedForms;
-                    for (auto&& frm : closed) {
-                        _projectTree->removeForm(frm);
-                        delete frm;
-                    }
-                    _closedForms.clear();
                     while (xml.readNextStartElement()) {
                         ProjectFormKind kind;
                         bool isForm = true;
@@ -2103,6 +2097,7 @@ bool AppProject::saveProject(const QString& filename)
         return false;
     }
 
+    setSavePath(QFileInfo(filename).absoluteDir().absolutePath());
     _projectFilename = absoluteFilename;
 
     QXmlStreamWriter w(&file);
diff --git a/src/appproject.h b/src/appproject.h
index c5fb6083..b9e7f157 100644
--- a/src/appproject.h
+++ b/src/appproject.h
@@ -97,6 +97,7 @@ class AppProject : public QObject
     void loadProject(const QString& filename);
     bool saveProject(const QString& filename);
     void restoreActiveWindows();
+    const QString & filePath() const noexcept { return _projectFilename; }
 
     // Called from MainWindow::~MainWindow() before delete ui.
     // Closes MDI windows and deletes forms/scripts without touching the project tree UI
diff --git a/src/mainwindow.cpp b/src/mainwindow.cpp
index cebf3694..1a1151d8 100644
--- a/src/mainwindow.cpp
+++ b/src/mainwindow.cpp
@@ -293,6 +293,7 @@ MainWindow::MainWindow(const QString& profile, bool useSession, const QString& s
     setWindowTitle(APP_PRODUCT_NAME);
     setUnifiedTitleAndToolBarOnMac(true);
     setStatusBar(new MainStatusBar(_mbMultiServer, this));
+    setAcceptDrops(true);
 
     if (auto* newButton = qobject_cast<QToolButton*>(ui->toolBarMain->widgetForAction(ui->actionNew))) {
         newButton->setMenu(ui->menuNew);
@@ -522,9 +523,6 @@ void MainWindow::on_outputDockVisibilityChanged(bool visible)
 ///
 void MainWindow::on_mdiSubWindowActivated(QMdiSubWindow* wnd)
 {
-    if(wnd)
-        markModified();
-
     QMdiSubWindow* stableWnd = ui->mdiArea->activeSubWindow();
     if(!stableWnd)
         stableWnd = ui->mdiArea->currentSubWindow();
@@ -693,12 +691,10 @@ void MainWindow::changeEvent(QEvent* event)
 ///
 void MainWindow::closeEvent(QCloseEvent *event)
 {
-    const bool shouldAskToSave = hasProjectContext() && (_isModified || _projectFilePath.isEmpty());
-    if(shouldAskToSave) {
-        if(!confirmSaveOnClose()) {
-            event->ignore();
-            return;
-        }
+    if (!confirmSaveOnClose()) {
+        // User canceled
+        event->ignore();
+        return;
     }
 
     saveAppSettings();
@@ -748,6 +744,47 @@ bool MainWindow::eventFilter(QObject* obj, QEvent* e)
     return QObject::eventFilter(obj, e);
 }
 
+void MainWindow::dragEnterEvent(QDragEnterEvent *event)
+{
+    const auto urls = event->mimeData()->urls();
+    if (!urls.empty()) {
+        if (QFile::exists(urls.front().toLocalFile())) {
+            event->acceptProposedAction();
+        }
+    }
+}
+
+void MainWindow::dropEvent(QDropEvent *event)
+{
+    const auto urls = event->mimeData()->urls();
+    if (!urls.empty()) {
+        auto replace = true;
+        if (hasProjectContext()) {
+            switch (QMessageBox::question(this, APP_PRODUCT_NAME,
+                tr("Would you like to combine the file(s) with the project?"),
+                QMessageBox::Yes | QMessageBox::No | QMessageBox::Cancel, QMessageBox::No)) {
+            case QMessageBox::Yes:
+                replace = false;
+                break;
+            case QMessageBox::No:
+                replace = true;
+                break;
+            default:
+                // User canceled
+                return;
+            }
+        }
+        for (const auto& url : urls) {
+            if (!loadProject(url.toLocalFile(), replace)) {
+                // User canceled
+                return;
+            }
+            replace = false;
+        }
+        event->acceptProposedAction();
+    }
+}
+
 ///
 /// \brief MainWindow::on_awake
 ///
@@ -931,11 +968,14 @@ void MainWindow::on_actionOpenProject_triggered()
     filters << tr("Project files (*.omsim)");
     filters << tr("All files (*)");
 
-    const auto filename = QFileDialog::getOpenFileName(this, QString(), _project->savePath(), filters.join(";;"));
-    if(filename.isEmpty()) return;
-
-    _project->setSavePath(QFileInfo(filename).absoluteDir().absolutePath());
-    loadProject(filename);
+    const auto filenames = QFileDialog::getOpenFileNames(this, QString(), _project->savePath(), filters.join(";;"));
+    auto replace = true;
+    for (const auto& filename : filenames) {
+        if (!loadProject(filename, replace)) {
+            return;
+        }
+        replace = false;
+    }
 }
 
 ///
@@ -943,13 +983,12 @@ void MainWindow::on_actionOpenProject_triggered()
 ///
 void MainWindow::on_actionSaveProject_triggered()
 {
-    if(_projectFilePath.isEmpty()) {
+    if (_project->filePath().isEmpty()) {
         on_actionSaveProjectAs_triggered();
         return;
     }
 
-    if(saveProject(_projectFilePath)) {
-        addRecentProject(_projectFilePath);
+    if (saveProject(_project->filePath())) {
         return;
     }
 
@@ -969,18 +1008,7 @@ void MainWindow::on_actionSaveProjectAs_triggered()
 ///
 void MainWindow::on_actionCloseProject_triggered()
 {
-    const bool shouldAskToSave = hasProjectContext() && (_isModified || _projectFilePath.isEmpty());
-    if(shouldAskToSave) {
-        if(!confirmSaveOnClose())
-            return;
-    }
-
-    _project->closeProject();
-    _projectFilePath.clear();
-    _lastProjectPath.clear();
-    _isModified = false;
-    updateProjectWindowTitle();
-    updateMainToolbarState();
+    closeProject();
 }
 
 ///
@@ -1524,29 +1552,29 @@ void MainWindow::presetRegs(QModbusDataUnit::RegisterType type)
 ///
 /// \brief MainWindow::loadProject
 /// \param filename
+/// \param replace
+/// \return
 ///
-void MainWindow::loadProject(const QString& filename)
+bool MainWindow::loadProject(const QString& filename, bool replace)
 {
-    if (hasProjectContext()) {
-        _project->closeProject();
-        _projectFilePath.clear();
-        _isModified = false;
-        updateProjectWindowTitle();
+    if (replace) {
+        if (!closeProject()) {
+            // User canceled
+            return false;
+        }
+        AppLogger::clear();
     }
 
-    AppLogger::clear();
-
     _project->loadProject(filename);
     applyGlobalAddressBase(AppPreferences::instance().globalAddressBase(), false);
     applyGlobalHexView(AppPreferences::instance().globalHexView(), false);
     syncGlobalViewControls();
-    _projectFilePath = QFileInfo(filename).absoluteFilePath();
-    _lastProjectPath = _projectFilePath;
-    _project->setSavePath(QFileInfo(filename).absoluteDir().absolutePath());
-    _isModified = false;
+    _isModified = !replace;
     updateProjectWindowTitle();
     updateMainToolbarState();
-    addRecentProject(_projectFilePath);
+    addRecentProject(_project->filePath());
+
+    return true;
 }
 
 ///
@@ -1558,11 +1586,28 @@ bool MainWindow::saveProject(const QString& filename)
     if (!_project->saveProject(filename))
         return false;
 
-    _projectFilePath = QFileInfo(filename).absoluteFilePath();
-    _lastProjectPath = _projectFilePath;
-    _project->setSavePath(QFileInfo(filename).absoluteDir().absolutePath());
     _isModified = false;
     updateProjectWindowTitle();
+    addRecentProject(_project->filePath());
+    return true;
+}
+
+///
+/// \brief MainWindow::closeProject
+/// \return
+///
+bool MainWindow::closeProject()
+{
+    if (!confirmSaveOnClose()) {
+        // User canceled
+        return false;
+    }
+
+    _project->closeProject();
+    _isModified = false;
+    updateProjectWindowTitle();
+    updateMainToolbarState();
+
     return true;
 }
 
@@ -1572,8 +1617,8 @@ bool MainWindow::saveProject(const QString& filename)
 ///
 QString MainWindow::projectName() const
 {
-    if(!_projectFilePath.isEmpty())
-        return QFileInfo(_projectFilePath).completeBaseName();
+    if (!_project->filePath().isEmpty())
+        return QFileInfo(_project->filePath()).completeBaseName();
 
     if(hasProjectContext())
         return tr("Untitled");
@@ -1592,7 +1637,7 @@ void MainWindow::updateProjectWindowTitle()
     if(name.isEmpty())
         setWindowTitle(modifiedMark + APP_PRODUCT_NAME);
     else
-        setWindowTitle(QString("%1%2 - %3").arg(modifiedMark, APP_PRODUCT_NAME, name));
+        setWindowTitle(QString("%1%2 - %3").arg(modifiedMark, name, APP_PRODUCT_NAME));
 }
 
 ///
@@ -1750,7 +1795,7 @@ void MainWindow::saveAppSettings()
     m.setValue("SavePath", _project->savePath());
     m.setValue(kNewFormKindKey, newFormKindToSetting(_newFormKind));
     m.setValue(kRecentProjectsKey, _recentProjects);
-    m.setValue(kLastProjectPathKey, _lastProjectPath);
+    m.setValue(kLastProjectPathKey, _project->filePath());
 }
 
 ///
@@ -1921,6 +1966,11 @@ void MainWindow::applyGlobalHexView(bool enabled, bool persist)
 ///
 bool MainWindow::confirmSaveOnClose()
 {
+    const auto shouldAskToSave = hasProjectContext() && (_isModified || _project->filePath().isEmpty());
+    if (!shouldAskToSave) {
+        return true;
+    }
+
     const auto button = QMessageBox::question(this,
                                               tr("Save Project"),
                                               tr("Save project before closing?"),
@@ -1932,9 +1982,8 @@ bool MainWindow::confirmSaveOnClose()
     if(button != QMessageBox::Save)
         return true;
 
-    if(!_projectFilePath.isEmpty()) {
-        if(saveProject(_projectFilePath)) {
-            addRecentProject(_projectFilePath);
+    if (!_project->filePath().isEmpty()) {
+        if (saveProject(_project->filePath())) {
             return true;
         }
 
@@ -1954,9 +2003,9 @@ bool MainWindow::promptSaveProjectAs(const QString& initialPath)
     QStringList filters;
     filters << tr("Project files (*.omsim)");
 
-    const QString defaultPath = _projectFilePath.isEmpty()
+    const QString defaultPath = _project->filePath().isEmpty()
         ? _project->savePath() + "/" + projectName() + ".omsim"
-        : _projectFilePath;
+        : _project->filePath();
     const QString dialogPath = initialPath.isEmpty() ? defaultPath : initialPath;
     auto filename = QFileDialog::getSaveFileName(this, QString(), dialogPath, filters.join(";;"));
 
@@ -1966,11 +2015,9 @@ bool MainWindow::promptSaveProjectAs(const QString& initialPath)
     if(!filename.endsWith(".omsim", Qt::CaseInsensitive))
         filename.append(".omsim");
 
-    _project->setSavePath(QFileInfo(filename).absoluteDir().absolutePath());
     if(!saveProject(filename))
         return false;
 
-    addRecentProject(QFileInfo(filename).absoluteFilePath());
     return true;
 }
 
@@ -1997,7 +2044,7 @@ QString MainWindow::projectSavePathInProfileDir() const
 ///
 bool MainWindow::hasProjectContext() const
 {
-    return !_projectFilePath.isEmpty()
+    return !_project->filePath().isEmpty()
         || _project->firstMdiChild() != nullptr
         || !_project->closedForms().isEmpty();
 }
diff --git a/src/mainwindow.h b/src/mainwindow.h
index 0330747c..17468330 100644
--- a/src/mainwindow.h
+++ b/src/mainwindow.h
@@ -58,8 +58,9 @@ class MainWindow : public QMainWindow
     void applyGlobalAddressBase(AddressBase base, bool persist = true);
     void applyGlobalHexView(bool enabled, bool persist = true);
 
-    void loadProject(const QString& filename);
+    bool loadProject(const QString& filename, bool replace = true);
     bool saveProject(const QString& filename);
+    bool closeProject();
 
     void appendConsoleMessage(const QString& source, const QString& text, ConsoleOutput::MessageType type);
     void showOutputConsole();
@@ -79,6 +80,8 @@ class MainWindow : public QMainWindow
     void changeEvent(QEvent* event) override;
     void closeEvent(QCloseEvent *event) override;
     bool eventFilter(QObject * obj, QEvent * e) override;
+    void dragEnterEvent(QDragEnterEvent *event) override;
+    void dropEvent(QDropEvent *event) override;
 
 public slots:
     void windowActivate(QMdiSubWindow* wnd);
@@ -206,7 +209,6 @@ private slots:
     QSharedPointer<QPrinter> _selectedPrinter;
     DataSimulator* _dataSimulator = nullptr;
     QString _profile;
-    QString _projectFilePath;
     ProjectFormKind _newFormKind = ProjectFormKind::Data;
     QStringList _recentProjects;
     QString _lastProjectPath;