Bundle Material does not show in Materials -field and in the Navigator with Qt 5.15 kit

Tested with Qt Design Studio 3.8 built with Qt 6.3.2 (snapshot 3)

When the bundle material is added to user materials, the bundle material goes invisible and does not show in the 3D object or in the Materials -field in the Material Browser -view. The warning message for the missing bundle material is shown in the picture below
NOTE: this happens if using the project with Qt 5.15 kit. Qt 6.3 kit worked.