My first idea is that you should include all results from the decisions instead of query the history. As a root decision, you can have a decision literal expression which invokes all decisions and collects the results.
Related posts:
- Results from multiple DMN tables
- New Release of the FEEL extension 1.5.0
- https://blog.camunda.com/post/2018/11/dmn-scala-extension/
Does this help you?
Best regards,
Philipp