The Header Bar helps you to navigate the object hierarchy of your model.
Qubicle 3.0 is node-based and supports object hierarchies. The right-most displayed object is always the one you are currently working on. Objects left of it display the path from the root node to the active node. Think of it as the bread crumb path usually found in website URLs.
To move up in the hierarchy:
Clickthe arrow button to move up one step
Clickon a node button to activate that node