Scratch that. I’ve now worked it out after checking out Mind map (tree chart) implementation (!) by @Paul_Danyliuk. Thanks Paul 
However, I’m now wondering if I’ve encountered a UI/layout limitation with using the single table?!?
Separate tables
When I had each entity in its own table, I was able create the following layout for a story record:
Sorry it’s so small, but I wanted to show the fact that there are separate buttons and sub-tables for scenarios (one entity) and tasks (another entity) visible in the one story record.
One table
If I use one table for all entities, I believe my only option is to have one sub-table with all the entities (potentially grouped by type):
If so, going back to @Federico_Stefanato’s classifications, I now feel that:
- From an interactive perspective, separate tables for each entity would be better
- From a semantic and informative perspective, I would prefer to have one table for all the entities
Have I missed anything?