[Remind-Fans] msgsuffix() type thing for calendar view?

[Tim Chase]

For the agenda-view, I have msgprefix()/msgsuffix() for tacking on
metadata for my tasks.

    FSET prefixcolor(x) iif( \
        x > $DefaultPrio, \
        iif($U == $T, c(BrRed), c(Red)), \
        iif(x < $DefaultPrio, c(Gry), c(Wht)))
    FSET fileprefix(x) upper(substr(filename(), strlen(remind_dir)+1, strlen(filename())-4))
    FSET msgprefix(x)  \
        prefixcolor(x) + \
        fileprefix(x) + \
        ": " + \
        c($DefaultColor)

This is handy for noting if it came from my birthday.rem vs my
anniversaries.rem file, so my agenda view might emit items like

  BIRTHDAY: Steve (27yo)
  BIRTHDAY: Doug (38yo)
  ANNIVERSARY: Ken & Ellen (15th)
  ADOPTION: Rachel (5yr)

However, when I use the calendar view, I didn't see an option for
annotating those differences.  So I was hoping to be able to do something like

    FSET calprefix(x) iif(icon=="", "", icon)

and then, say, in my birthday.rem put

    SET icon "🎁"

to prefix all birthdays with a gift emoji.  Any recommendations on
how to get such a behavior?

Thanks!

-tim