GUI in 3D: Always process GUI even when the scene tree is paused

viewport/gui_in_3d/gui_panel_3d.tscn

@@ -19,6 +19,7 @@ albedo_texture = SubResource( "2" )
 size = Vector3(3, 2, 0.1)
 
 [node name="GUIPanel3D" type="Node3D"]
+process_mode = 3
 script = ExtResource( "1" )
 
 [node name="SubViewport" type="SubViewport" parent="."]