diff --git a/sources/TerminalStrip/ui/terminalstripeditorwindow.cpp b/sources/TerminalStrip/ui/terminalstripeditorwindow.cpp
index cc1d86a94..ef7538c49 100644
--- a/sources/TerminalStrip/ui/terminalstripeditorwindow.cpp
+++ b/sources/TerminalStrip/ui/terminalstripeditorwindow.cpp
@@ -52,6 +52,8 @@ TerminalStripEditorWindow *TerminalStripEditorWindow::instance(QETProject *proje
 {
 	QProgressDialog busy_(tr("Opening the terminal block manager..."), QString(), 0, 0, parent);
 	busy_.setWindowTitle(tr("Terminal block manager"));
+		//Only a title : nothing to minimize, maximize or close
+	busy_.setWindowFlags(Qt::Dialog | Qt::CustomizeWindowHint | Qt::WindowTitleHint);
 	busy_.setWindowModality(Qt::ApplicationModal);
 	busy_.setCancelButton(nullptr);
 	busy_.setMinimumDuration(0);
@@ -74,6 +76,23 @@ TerminalStripEditorWindow *TerminalStripEditorWindow::instance(QETProject *proje
 	QCoreApplication::processEvents(QEventLoop::ExcludeUserInputEvents);
 	QApplication::setOverrideCursor(Qt::WaitCursor);
 
+		//The folios not built yet (lazy folios) are built now : show the
+		//progress, and run the event loop between two folios, so that the
+		//window system still gets answers (else the message is said
+		//"not responding")
+	if (project)
+	{
+		project->setFolioBuildObserver([&busy_](int built, int total)
+		{
+			if (busy_.maximum() != total) {
+				busy_.setMaximum(total);
+			}
+			busy_.setLabelText(tr("Reading folio %1 of %2...").arg(built).arg(total));
+			busy_.setValue(built);
+			QCoreApplication::processEvents(QEventLoop::ExcludeUserInputEvents);
+		});
+	}
+
 	static QMutex mutex_;
 	if (!window_) {
 		mutex_.lock();
@@ -84,6 +103,9 @@ TerminalStripEditorWindow *TerminalStripEditorWindow::instance(QETProject *proje
 		window_->setProject(project);
 	}
 
+	if (project) {
+		project->setFolioBuildObserver({});
+	}
 	QApplication::restoreOverrideCursor();
 	return window_;
 }
diff --git a/sources/qetproject.cpp b/sources/qetproject.cpp
index c63d09602..23034f30e 100644
--- a/sources/qetproject.cpp
+++ b/sources/qetproject.cpp
@@ -407,6 +407,11 @@ void QETProject::init()
 		m_autosave_timer.setInterval(ms);
 		connect(&m_autosave_timer, &QTimer::timeout, this, [this]()
 		{
+				//Not while folios are being built (the event loop can run
+				//then, see setFolioBuildObserver()) : the next time
+			if (this->m_state == ProjectParsingRunning) {
+				return;
+			}
 			if(!this->m_file_path.isEmpty())
 			{
 					//No one is there to ask: a file changed behind this
@@ -762,6 +767,18 @@ void QETProject::loadFolios() const
 	buildFolios(m_diagrams_list);
 }
 
+/**
+	@brief QETProject::setFolioBuildObserver
+	@p observer is called after each folio built by buildFolios(), with the
+	number of folios built so far and the number to build : a long build
+	can show its progress, and keep the window system answered by running
+	the event loop (without the user input) in @p observer. The autosave
+	waits meanwhile. An empty function removes the observer.
+*/
+void QETProject::setFolioBuildObserver(std::function<void (int, int)> observer) {
+	m_folio_build_observer = std::move(observer);
+}
+
 /**
 	@brief QETProject::buildFolios
 	Build those of @p folios still waiting, as opening builds them: all
@@ -785,8 +802,23 @@ void QETProject::buildFolios(const QList<Diagram *> &folios) const
 	const bool signals_were_blocked = self->m_data_base.signalsBlocked();
 	self->m_data_base.blockSignals(true);
 	QList<Diagram *> built;
+	int waiting_ = 0;
+	if (m_folio_build_observer) {
+		for (Diagram *d : folios)
+			if (!d->isLoaded()) ++waiting_;
+	}
 	for (Diagram *d : folios)
-		if (d->buildDeferred()) built << d;
+	{
+		if (d->buildDeferred())
+		{
+			built << d;
+				//Someone shows the progress (a long build, opening the
+				//terminal block manager...)
+			if (m_folio_build_observer) {
+				m_folio_build_observer(built.size(), waiting_);
+			}
+		}
+	}
 	for (Diagram *d : std::as_const(built))
 		self->folioLoaded(d);
 	self->m_data_base.blockSignals(signals_were_blocked);
diff --git a/sources/qetproject.h b/sources/qetproject.h
index aeb87a1b5..437112fcf 100644
--- a/sources/qetproject.h
+++ b/sources/qetproject.h
@@ -18,6 +18,7 @@
 #ifndef QET_PROJECT_H
 #define QET_PROJECT_H
 
+#include <functional>
 #include "ElementsCollection/elementslocation.h"
 #include "NameList/nameslist.h"
 #include "project/projectpropertieshandler.h"
@@ -150,6 +151,7 @@ class QETProject : public QObject
 		QSet<Diagram *> tableChainFolios(Diagram *folio) const;
 		void loadFolios() const;
 		void buildFolios(const QList<Diagram *> &folios) const;
+		void setFolioBuildObserver(std::function<void(int, int)> observer);
 		void folioLoaded(Diagram *folio);
 		int folioIndex(const Diagram *) const;
 		XmlElementCollection *embeddedElementCollection()const;
@@ -625,6 +627,8 @@ class QETProject : public QObject
 		QHash<QUuid, std::pair<int, int>> m_shared_uuid_keepers;	//symbol and wire uuids the file carries, see derivedItemUuid()
 		projectDataBase m_data_base;
 		QVector<TerminalStrip *> m_terminal_strip_vector;
+			//Called after each folio built, see setFolioBuildObserver()
+		std::function<void(int, int)> m_folio_build_observer;
 		QVector<Cable *> m_cables;
 
 		ProjectPropertiesHandler m_project_properties_handler;