In the configuration tool, using either the cubeMX-IDE or the older tool, do a control left click on the pin in question. That should cause the alternate pins for the function to blink. As an example, SPI5-MISO on the F767 has a pin to the left side of the chip, and also one to the bottom.
For any function and any chip:
the configuration generator reads the assigned functions from the chip model. You can only select legal functions for any pin. The "produce code" generates user pin named definitions in main.h. Look for stm32xxxxxxx_hal_msp.c in the core/source directory. Replace the xxxxxx by something appropriate to your processor. Check the inits, and you will find where the configuration tool defines the pin functions for the processor.
You do NOT need to mess with this. If you're using the MX configuration tools, defining the alternate functions at that level and in that application will work for you.
If you are designing your own board, you have the most flexibility. If you use a Nucleo board, then you have less, but the alternate functions will likely be different for each project. If you use a Discovery board, be aware that the default setups (say for FMC on the 459i Disco board) are not used without modification, there's an alternate pin used.
So: only your user named pins are in main.h.
Use the configuration tool (even when using BSP drivers) to assign alternate pins.
Mixing BSP drivers on DISCO boards with cubeMX drivers is another issue entirely.
