For completeness, we probably want to provide API for these recently added enumerated properties. However, we might want to wait until they are not "provisional" properties any more; or at least, keep the API @draft while they are.
Implementation-wise, see if it's better to a) widen the uprops.icu properties vectors (adding 4+5 bits) or b) have a simple/special data structure like for the Joining_Group.
One of these got renamed. Adjusted the summary.
See also for Vertical_Orientation, another layout property.
One part of is another version of this ticket.
I am seeing more requests for these properties lately.