At first glance it looks like there is currently no support for F29+ in JMRI, for any system (sigh of relief that it's not a SPROG problem), but I could yet be proven wrong, they may be handled differently in different code that I haven't seen yet.
I have asked the question of the other developers.
Which decoder is involved? Is there any function remapping for these functions, that would allow you to access them, at the expense of other, lower numbered, functions?
Andrew