Schematic, hypergraph, or watever fancy name to a hierarchy viewer ;) — Right-Click Select
How to PARENT and UNPARENT objects in Blender }
Collections not Groups – Blender Knowledgebase
Blender: How to Group Objects – Simply Explained | All3DP
selection tools - I have a large scene with a hierarchy of nested Empties. I need to select and delete all the objects under Empties with a specific name - Blender Stack Exchange