Make sure to plan your upgrade to 12.1, 12.0 is now end-of-life.my box is FreeBSD 12.0-RELEASE
FreeBSD's PF was imported from OpenBSD 4.7 (or was it 4.6?). In any case, OpenBSD's PF is a lot newer and therefor may have features FreeBSD's PF doesn't have.
Make sure to plan your upgrade to 12.1, 12.0 is now end-of-life.
if you wanna stay with FreeBSD you could have a look at the functionality of ipfw(8) and divert(4)