The Set Up Allowance Plan Adjustment task is specifically designed to update allowance plan amounts for existing employee assignments when plan targets change. Simply editing the allowance plan amount ensures new employees receive the updated value, but it does not automatically update existing employees already assigned to the plan.

By running the Allowance Plan Adjustment task and selecting Adjust to New Defaults, Workday evaluates all employees assigned to the plan and updates their allowance amounts to match the new default value of $3,500.

Manually updating employees through Request Compensation Change is inefficient and error-prone. Creating a new plan introduces unnecessary complexity and disrupts reporting continuity.

Therefore, the correct and Workday-recommended approach is to run Set Up Allowance Plan Adjustment and adjust to new defaults, making option D correct.