IPv6 interface identifier/index on FreeBSD?

So, moving to a dynamic IPv6 network, I want to be able to address my hosts
both predictably (for which eui64/RA has been working), and also statically
in some cases.  For a dynamic network/subnet, an IPv6 address can be specified
by the “subnet prefix” and "interface identifier” (or “interface index”
according to ifconfig’s man page re: eui64).  Linux systems seem(ed) to call
this “token”, and it can be set for an interface (ip token set).

Is it possible to do this on FreeBSD?  Searching the ifconfig man page on
FreeBSD 14 I don’t _see_ anything other than eui64 that mentions this.
If there isn’t a reason to allow setting the IID on an interface in FreeBSD,
was that decision made for a reason?

Then, after that is the more complicated situation that I want to apply
multiple IID’s across multiple aliases on the same interface.  That may
or may not be reasonable, but will be my next question.  Sub-interfaces
or alias interfaces maybe?

Thank you.

                 - Chris