Hi,
Sorry, unfortunately the ST’s SVD files (files with register definitions) do not include much details, so our BSP building logic uses some heuristics to extract this information from ST’s header files. This process is not perfect and it may skip some definitions, but unfortunately there is no better source for subregister information.
Our best advice would be to locate and patch the corresponding definition file in %LOCALAPPDATA%\VisualGDB\EmbeddedBSPs\arm-eabi\com.sysprogs.arm.stm32\<family>\DeviceDefinitions (you can keep the unzipped file in place and it will override the .xml.gz file automatically).