Custom worktags extend Workday's delivered set of accounting dimensions, such as cost center and fund, allowing organizations to capture additional reporting and routing attributes specific to their business. The Official Workday Pro Procure-to-Pay Guide explains that custom worktags can be incorporated into Account Posting Rules and condition rules, enabling transactions tagged with specific custom worktag values to be automatically routed to particular general ledger accounts, which is the function of accounting routing. Option B is incorrect because security assignments in Workday are governed by security groups, roles, and domain or business process security policies, none of which rely on custom worktags. Option C is incorrect because worker assignments are managed through supervisory organizations and staffing models within Human Capital Management, not through custom worktags. Option D is incorrect because hierarchical structure is a characteristic of organizations, such as cost center or company hierarchies, which custom worktags do not themselves create; worktags are flat values used for tagging transactions rather than structural containers with parent-child relationships.