What parenthetical notation should be used to indicate a lengthy pause during proceedings?

The correct choice to indicate a lengthy pause during proceedings is represented by the notation "At sidebar on the record." This phrase provides a clear contextual reference for the pause, indicating that the discussion was held in the sidebar setting but is still part of the official record.

Using this notation helps maintain the integrity and clarity of the transcript. It assures the reader that while the parties may have stepped aside momentarily, the dialogue under consideration remains documented and relevant to the proceedings. This level of detail is essential for accurately portraying the flow of events within a legal context.

The other options may refer to conversations held in different contexts, such as off the record or at the end of discussions, which could lead to ambiguity about the content and significance of those pauses. Therefore, using the phrase about the sidebar ensures that the pause is recognized as a governed and documented part of the proceedings.