A sentence can be vivid, accurate and completely wrong for the draft around it. Moving it elsewhere is not the same as deciding it has no value.
Identify the paragraph where the piece repeatedly loses direction. Underline the sentence you are most reluctant to cut and ask what question it opens. Compare that question with the one the current draft is trying to answer.
If they differ, copy the sentence into a separate working note with a line explaining its possible use. Keep enough context to understand it later, but do not copy the whole draft just to avoid making a decision.
Read the original paragraph without the sentence. Does the argument become clearer? Is a necessary transition now missing, or merely an attractive detour? Repair only what the paragraph still needs.
For example, an essay about repairing a chair might contain a compelling memory of a train journey. The shared person in both scenes may not be enough to justify the detour. The journey could open another piece with its own purpose.
Revisit the saved note after finishing the current draft. Some fragments will grow; others will remain fragments. The immediate benefit is a piece that follows its own question without requiring every good sentence to travel with it.
Image: an editorial illustration, not a documentary photograph.