The function "NavigationWidget::updateToggleText()" also set the text for action.

--- src/plugins/coreplugin/navigationwidget.cpp
+++ src/plugins/coreplugin/navigationwidget.cpp
@@ -293,11 +293,13 @@ void NavigationWidget::updateToggleText()
     d->m_toggleSideBarAction->setVisible(haveData);
     d->m_toggleSideBarAction->setEnabled(haveData && NavigationWidgetPlaceHolder::current(d->m_side));
 
-    const char *trToolTip = d->m_side == Side::Left
-                                ? (isShown() ? Constants::TR_HIDE_LEFT_SIDEBAR : Constants::TR_SHOW_LEFT_SIDEBAR)
-                                : (isShown() ? Constants::TR_HIDE_RIGHT_SIDEBAR : Constants::TR_SHOW_RIGHT_SIDEBAR);
+    const char *trText = d->m_side == Side::Left
+                             ? (isShown() ? Constants::TR_HIDE_LEFT_SIDEBAR : Constants::TR_SHOW_LEFT_SIDEBAR)
+                             : (isShown() ? Constants::TR_HIDE_RIGHT_SIDEBAR : Constants::TR_SHOW_RIGHT_SIDEBAR);
+    QString text = QCoreApplication::translate("Core", trText);
 
-    d->m_toggleSideBarAction->setToolTip(QCoreApplication::translate("Core", trToolTip));
+    d->m_toggleSideBarAction->setText(text);
+    d->m_toggleSideBarAction->setToolTip(text);
 }
 
 void NavigationWidget::placeHolderChanged(NavigationWidgetPlaceHolder *holder)