Hi,
Normally, it should work automatically, since both bootloader and the main application will end up calling InitializeFastSemihosting() that passes the semihosting buffer location to VisualGDB.
However, it only works if the memory location of the buffer is the same between the bootloader and the main application (achievable via linker scripts).
If the addresses are different, please try this build: VisualGDB-6.0.4.5057.msi