Thank you Fabio. I see you commented out the Identity piece but I DO need that.
It appears that using it ALMOST works; when the H2 instance is created, the entityId field is marked as the Identity column as noted in the create table statement in the description. But since i marked the eventMilestoneId field as the Identity column, it should create the table with that as the Identity column instead of the eventId.

This is what should be generated:

create table evnt_milstn (
  evnt_id bigint not null,
  evnt_milstn_id bigint generated by default as identity not null,
  primary key (evnt_id, evnt_milstn_id)
)