Is it possible to customize the loader.conf file before boot?

I am trying to compile software (designed for Linux) that requires uhid. I'm new to FreeBSD, but I believe I have to modify the loader.conf file before boot to get this to work. https://man.freebsd.org/cgi/man.cgi?query=uhid