Which approach allows for the adjustment of reference planes using a subcategory?

The approach that allows for the adjustment of reference planes using a subcategory is visibility management. This feature in Revit enables users to control what elements are visible in different views by assigning them to specific subcategories. Reference planes can be categorized under these subcategories so that they can be turned on or off in views, or adjusted in terms of display properties like color, line style, and visibility.

Visibility management ensures that the designer has greater control over their project environment by allowing them to focus on specific elements while hiding others, which is particularly useful when working on complex designs. With subcategories, it’s easier to organize and manage the visibility of various reference planes based on the needs of the project or the specific design phase, thus enhancing overall workflow efficiency.

The other options, such as layer designation, subcategory grouping, and color assignment, do not specifically entail the functionality of adjusting visibility and properties of reference planes in the same way that visibility management does.