What are you asking? Be more explicit and verbose.
I am using a Bluetooth keyboard, it has a FN key. I want started the windows system, it's locked (pushed state). it can set this option in the BIOS with notebook. So NUC's BIOS can add this settings?
Modern notebooks have an option in BIOS for enabling the FN keys functionality in order to either use the normal FN key(s) or to lock them.
In the Intel® NUC's case they are not designed with an embedded keyboard, thus wireless Bluetooth keyboards should have an original equipment manufacturer(OEM) software or driver which allows you to lock/unlock the FN keys.