From a related list, what would a user click to personalize the layout of the columns?

The Gear icon (often called the 'personalize list' or 'configure list' icon) is a standard user interface element in ServiceNow lists and related lists. Clicking this icon allows users to open a dialog box where they can select which columns to display, their order, and other list preferences, thereby personalizing the list layout.

A Context Menu (right-click menu) offers various actions on selected items or the list itself, but direct column personalization is typically handled by the Gear icon.

A Pencil icon usually signifies editing the data within a record or a specific item's properties, not the structural layout of a list.

A Magnifier icon is used for searching within a list, not for customizing its column layout.