It all depends on on the exact BIOS.
I suggest you ask this question on a BIOS modding forum.
You will need to provide them with the Exact BIOS (with a link to download it), so they can determine if it is possible.
I personally have unlocked hidden options in some OEM BIOS in the past but I no longer do BIOS mods.
That's what BIOS passwords are for. You cannot hide things in the manner in which you are asking.
It all depends on on the exact BIOS.
I suggest you ask this question on a BIOS modding forum.
You will need to provide them with the Exact BIOS (with a link to download it), so they can determine if it is possible.
I personally have unlocked hidden options in some OEM BIOS in the past but I no longer do BIOS mods.