This editor extension simply shows whether or not the prefab instances in Hierarchy Window are identical to the original 'Prefab' in terms of a property or component. If one of properties is changed or a component is added/deleted, the check mark beside the prefab instance would change to exclamation mark which means something is different from the original prefab. That is, it prevents users from changing property values accidentally or forgetting to click apply button to apply changes to the original prefab.

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