What is the ideal way to assign sequence numbers for this hierarchy?

Summary:

Level	Hierarchy					Sequence Number
Level 1	Root					1
Level 2		Model 1				2
Level 3			Sub Parent 1			3
Level 4				Child 1		4
Level 5					Grand Child	5
Level 3			Sub Parent 2			6
Level 4				Child 2		7
Level 5					Grand Child	8
Level 2		Model 2				9
Level 3			Sub Parent 5			10
Level 4				Child 5		11
Level 5					Grand Child	12

The configurator has one root, which contains multiple models. Each model contains several sub-parents, each sub-parent contains multiple child items, and each child contains multiple grandchild items.

What is the ideal way to assign sequence numbers for this hierarchy?
Should the sequence follow a simple incremental order like 1, 2, 3, 4, …, or is there a recommended best practice for numbering such hierarchical structures?

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