Unfortunately, there is currently not a way to do this. But perhaps in the future I may add it, if I can figure out a sane interface and implementation to do such a thing. Maybe I will add a trigger that will make the output show differently.
Although I may be new to StackExchange, I am the author of ftrace (real name Steven Rostedt - look up the git history). The "real answer" will happen when I write the code!