"For any other question related to the STM32F4 product, the hardware performance, the hardware characteristics, the tools, the environment, you can submit a topic on the ST Community/STM32 MCUs forum".
This is what I did reporting in STM32 MCU forum about CubeMX v1.5.2 not allowing to choose previously used firmware library STM32F4_v1.23.0. Did not do any good - no reply
Thank you @Amel Nasri for your advice. This indeed may increase chances of "visibility". If reporting a bug in STM software is done by "tagging" the "bug report" as one of many forum topic, this confirms that STM employees do not collect them to work on.