When you have nested focusable components (e.g., a dialog inside another dialog), focus should stay inside the currently active (topmost) scope. Closing a scope should return focus to the previous one.
pushFocusScope(container) pushes a new scope onto the stack and traps focus inside that container. The returned function pops
the scope and restores focus to the previously focused element. Only the topmost scope traps focus.
NestedDialog, MultiLevelModal, Wizard, Stepper, ComplexForm