In Part Structure Compare a WTPart that was replaced by another is shown on the same line with a specific icon. This helps to understand the changes to a structure very quickly. Unfortunately this only happens if a specific criteria is meet. This criteria is a hidden value called ComponentID on the UsageLink. It remains the same if a part is e.g. replaced by the replace with existing action. However it changes if the replacement is driven from CAD or if a user removes a UsageLink and adds a new one with the same LineNumber or FindNumber.
There is a supported Customization point that will allow to show UsageLinks with the same LineNumber in one row. However the replacement Icon is still only show if the ComponentID match. So it would be really helpful to modify the criteria for a replacement. That would help to identify replacements in big structures even if they are resulting from User Actions.