How to identify and replace/apply the 100% matches while proofreading/editing?

Friends, Could you please tell me the method to identify and replace/apply the 100% matches while proofreading/editing.

Suppose, I am editing a document which contains 100 sentences out of which 8 are same. I edit one of these 8 sentences and the second same sentence is presented after so many sentences. I can’t exactly remember what edits I made to the earlier same sentence. Is there a method to locate the first same edited sentence and then replace/apply/use it when the same sentence is being edited?

Thanks in advance for your valuable suggestions.