Index: /applications/editors/josm/plugins/flatlaf/ivy.xml
===================================================================
--- /applications/editors/josm/plugins/flatlaf/ivy.xml	(revision 35678)
+++ /applications/editors/josm/plugins/flatlaf/ivy.xml	(revision 35679)
@@ -2,5 +2,5 @@
   <info organisation="org.openstreetmap.josm.plugins" module="flatlaf"/>
   <dependencies>
-    <dependency conf="default->default" org="com.formdev" name="flatlaf" rev="0.44"/>
+    <dependency conf="default->default" org="com.formdev" name="flatlaf" rev="0.45"/>
   </dependencies>
 </ivy-module>
Index: /applications/editors/josm/plugins/flatlaf/src/org/openstreetmap/josm/plugins/flatlaf/FlatLaf.properties
===================================================================
--- /applications/editors/josm/plugins/flatlaf/src/org/openstreetmap/josm/plugins/flatlaf/FlatLaf.properties	(revision 35679)
+++ /applications/editors/josm/plugins/flatlaf/src/org/openstreetmap/josm/plugins/flatlaf/FlatLaf.properties	(revision 35679)
@@ -0,0 +1,5 @@
+#
+# License: GPL. For details, see LICENSE file.
+#
+
+TabbedPaneUI=org.openstreetmap.josm.plugins.flatlaf.JosmFlatTabbedPaneUI
Index: /applications/editors/josm/plugins/flatlaf/src/org/openstreetmap/josm/plugins/flatlaf/JosmFlatTabbedPaneUI.java
===================================================================
--- /applications/editors/josm/plugins/flatlaf/src/org/openstreetmap/josm/plugins/flatlaf/JosmFlatTabbedPaneUI.java	(revision 35679)
+++ /applications/editors/josm/plugins/flatlaf/src/org/openstreetmap/josm/plugins/flatlaf/JosmFlatTabbedPaneUI.java	(revision 35679)
@@ -0,0 +1,48 @@
+// License: GPL. For details, see LICENSE file.
+package org.openstreetmap.josm.plugins.flatlaf;
+
+import java.beans.PropertyChangeEvent;
+import java.beans.PropertyChangeListener;
+
+import javax.swing.JComponent;
+import javax.swing.plaf.ComponentUI;
+
+import org.openstreetmap.josm.gui.widgets.HideableTabbedPane;
+import com.formdev.flatlaf.ui.FlatTabbedPaneUI;
+
+/**
+ * Special JOSM UI delegate for JTabbedPane that supports hiding tab area for {@link HideableTabbedPane}.
+ */
+public class JosmFlatTabbedPaneUI extends FlatTabbedPaneUI {
+    public static ComponentUI createUI(JComponent c) {
+        return (c instanceof HideableTabbedPane)
+            ? new JosmFlatTabbedPaneUI()
+            : FlatTabbedPaneUI.createUI(c);
+    }
+
+    @Override
+    public void uninstallUI(JComponent c) {
+        super.uninstallUI(c);
+
+        // HideableTabbedPane replaces FlatTabbedPaneUI with its own implementation
+        // based on BasicTabbedPaneUI. This listener detects this, sets a FlatLaf client
+        // property to enabed tab area hiding, and then resets the UI delegate to FlatTabbedPaneUI.
+        PropertyChangeListener l = new PropertyChangeListener() {
+            @Override
+            public void propertyChange(PropertyChangeEvent e) {
+                c.removePropertyChangeListener("UI", this);
+
+                if (e.getOldValue() instanceof FlatTabbedPaneUI &&
+                    e.getNewValue() != null &&
+                    e.getNewValue().getClass().getName().startsWith(HideableTabbedPane.class.getName()+'$'))
+                {
+                    c.putClientProperty("JTabbedPane.hideTabAreaWithOneTab", true);
+
+                    // reset to FlatTabbedPaneUI
+                    c.updateUI();
+                }
+            }
+        };
+        c.addPropertyChangeListener("UI", l);
+    }
+}