And the final idea was to propose to extend the Note table with addtional related events fields.
@MPhilofsky, according to your use case, do you think, instead of using fact_relationship table, it would be better to have related_event_id, related_domain_id fields in Observation table where you can put your additional concepts?
@Christian_Reich, is it possible to extend Measurement, Observation, Condition, Procedure tables with related_event_id, related_domain_id fields?